TEXT: 5.0 Converting to Arms Law from
  Other Systems
  5.1 Dungeons & Dragons Third edition®
  (D20®)
  It is very easy to adapt the latest version of Dungeons & Dragons
  (D&D) and Arms Law to work together as they use almost the same
  type of mechanics, with the major difference being one of scale.
  Armor Type
  The easiest method of determining a character’s Armor Type
  (AT) is through comparing a description of the armor worn against
  the armor descriptions in Section 1.1 and choosing the one that
  matches best. If the armor is masterwork or magical in nature, the
  bonus is multiplied by 5 and added to the Defensive Bonus.
  Defensive Bonus
  To determine a character’s Defensive Bonus (DB), use the
  following guidelines, adding together all applicable items.
  Stat Bonus – Take the character’s Dexterity bonus, double it, and
  then multiply the result by 3 and add it to the Defensive bonus.
  Shields – A shield adds a straight bonus to DB. Use the Defensive
  Bonus chart to determine the bonus gained by the type of shield
  being used. See the next item for masterwork and magical shields.
  Masterwork or Magical Armor and Shields – For each +1 (magical
  or masterwork) of the armor/shield, add +5 to the character’s
  DB.
  Special Bonuses – For each additional +1 received from a special
  bonus of any sort, add another +5 to the DB.
  Offensive Bonus
  To determine your Offensive Bonus (OB), use the following
  guidelines, adding together all applicable items.
  Base Attack Bonus – For each +1 of your base attack bonus, add
  +10 to your OB.
  Stats –  Take the character’s appropriate stat bonus (Strength for
  melee, Dexterity for missiles), double it, and then multiply the
  result by 3 and add it to the OB.
  Masterwork or Magical weapons – For each additional +1 received
  from magical or masterwork items, add +5 to your OB.
  Special Bonuses – For each additional +1 received from a special
  bonus of any sort, add another +5 to the OB.
  Concussion Hits
  Arms Law is designed for a system in which a normal fighter will
  take around 100 hits by tenth level. To accommodate this, just
  multiply your character’s hit points by 2 and add 10 to the result.
  Damage From Spells
  For damage that results from the effects of a spell, or special
  ability, just double the amount of damage received for use with
  this system.
  General
  All other facets remain essentially the same for the rest of the
  system.
  The beauty of the Arms Law system is that it will work with any
  role playing system you are using. However, conversion of certain
  stats may appear to be a problem. This section will attempt to assist
  you in converting to Arms Law from several popular systems.
  Arms Law works best when using it with systems that include
  such combat results as stuns and activity penalties. The results for
  specific criticals can then be more easily translated into results of
  your system of choice.
  For conversion to any system, remember: the effectiveness,
  flexibility, and power of an attack is entirely contained within the
  offensive bonus of an attacker. So the offensive bonus should
  represent the potential of the attacker for inflicting damage. Find
  your system below and follow the simple steps. If you do not see
  your system, look for a system that is similar to it.
  Note: This combat system tends to focus on realistically deadly combat.
  If your RPG assumes a relatively non-lethal combat situation (e.g.,
  most super hero games), usage of this system may not be healthy for
  your characters!
  As a final observation, we want to point out that many systems
  put arbitrary limits on your characters that force them to perform
  in certain ways (e.g., your thief cannot wear plate armor or use a
  two-hand weapon). We believe these limitations to be unrealistic.
  We do suggest that you use whatever system you are having fun
  with, but for
  r e a l i s t i c
  characters, you
  should check
  into Rolemaster
  Fantasy Role
  Playing or the
  u p c o m i n g
  HARP: High
  Adventure Role
  Playing.
  78
  Stat Conversion Table
  1-20
  3-18
  RM
  RM
  Stat
  Stat
  Stat
  Bonus
  0
  0
  1
  -10
  1
  1
  2
  -9
  2
  2
  4
  -8
  3
  3
  6
  -7
  4
  4
  8
  -6
  5
  5
  10
  -5
  6
  6
  15
  -4
  7
  7
  20
  -3
  8
  8
  25
  -2
  9
  9
  30
  -1
  10
  10
  50
  0
  11
  11
  70
  1
  12
  12
  75
  2
  13
  13
  80
  3
  14
  14
  85
  4
  15
  15
  90
  5
  16
  16
  92
  6
  17
  17
  94
  7
  18
  18
  96
  8
  19
  19
  98
  9
  20-21
  20-21
  100
  10
  22-23
  22-23
  101
  12
  24-25
  24-25
  102
  14
  
  5.2 Advanced Dungeons & Dragons®
  Take your AD&D game to the next level by creating critically lethal
  combats!
  Armor Type
  Armor Types are easy enough to translate by description (ignoring
  the AC that the armor gives you). An important note is that
  “magical” armor in AD&D gives you a better class of armor. In this
  system, enchanted items give bonuses (enchanted armor, helms,
  shields, and greaves generally give bonuses to DB).
  Attack Type
  Once again, this is simple enough to convert by simply using the
  description of the attack.
  For non-weapon attacks this can be trickier. There is no weapon
  table that compares to a fire-breathing dragon or a lightning-bolt
  casting wizard. For these attacks you need to determine two things:
  an attack table and a critical table.
  The attack table should be one where the damage is roughly
  equivalent in AD&D. If the attack does about as much damage as a
  two-handed sword, use the same attack table and modifications as
  a two-handed sword. If there is no comparable weapon, use a
  relatively equivalent table. So if an attack does twice as much
  damage as a two-handed sword, use an attack table that does twice
  as much damage as the table for a two-handed sword. For these
  comparisons use the maximum value for Rigid Leather (Light).
  The critical table should follow common sense. Heat, Cold and
  Electricity criticals were included for fireballs, undead cold-attacks,
  and lightning-bolts. Air and earth based elemental attacks will
  generally use Krush criticals. For other attacks use your best
  judgment.
  Offensive Bonus
  This is a bit trickier. There is some actual calculation that must
  be done. Follow the steps below to determine your character’s basic
  OB.
  •
  Start by multiplying your level times 5.
  •
  To this number add +20 if you are a Warrior; +10 if you are a
  Rogue; or +5 if you are a Priest.
  •
  Add another +5 for each +1 bonus to Hit gained from Strength.
  Also do this for each +1 bonus to Hit from Dexterity.
  •
  Because attacks are based upon different weapon types, add
  another +20 if you have a weapon proficiency in the attack type.
  Defensive Bonus
  This is actually pretty simple. All characters start with a basic
  DB of zero. Shields apply as listed in Section 3.0 (and other
  modifiers from Section 3.0 may be appropriate). Then apply the
  following modifiers.
  •
  Gain a +5 for each +1 to AC from Dexterity.
  •
  Gain a +5 for each +1 bonus to AC from armor or any other
  item.
  Concussion Hits
  Once again, this is pretty simple. Take your Hit Points from AD&D
  and multiply them times 3. Add +10 to this total and that is your
  total number of concussion hits in this system.
  5.3 GURPS®
  GURPS is actually very similar to Rolemaster in many ways, which
  makes it easy to convert the two systems.
  Armor Type
  Armor is very descriptive in GURPS, so you can just compare the
  GURPS armor to the descriptions in Section 1.1.
  Attack Type
  Attack types for characters are again simple, converting the
  weapon used in GURPS to the appropriate table in this book. Being
  a universal system, GURPS sometimes incorporates fantasy
  elements. Refer to the section on AD&D to convert fantasy attacks
  to these tables.
  Offensive Bonus
  OB is simply five times the appropriate GURPS skill level, minus
  ten.
  Defensive Bonus
  DB is equal to your dodge. Parry comes into play as a portion of
  your offensive bonus, and Block is an addition to your DB based
  on your shield type (Section 3.4).
  Concussion Hits
  To convert GURPS hits to this system, multiply them by five and
  add 20.
  5.4 Legend of the Five Rings™
  Legend of the Five Rings uses a dice pool system, which makes
  conversions to a Rolemaster system rather complicated. Rather than
  give a chart of the possible dice pools and their OB/DB equivalents,
  this section shows how to convert the results achieved using L5R
  dice pools to ones usable with the tables in this book.
  Armor Type
  Heavy samurai armor would be considered Chainmail (Heavy),
  while light samurai armor would be Rigid Leather (Light). Other
  defensive capabilities should be converted using the descriptions
  in Section 2.1.
  Attack Type
  Most of the weapons for L5R are listed in the attack tables of this
  book. For ones not listed, go by the descriptions in Section 2.2, or
  use a similar weapon listed on one of the tables.
  Offensive Bonus
  Roll for the attack as normal, but multiply the result by 6. This is
  the number to reference on the appropriate weapon attack table.
  For raises, subtract five from your roll before multiplying, but
  increase the critical two levels. Roll any criticals with percentile
  dice.
  Note: This gives a limited number of results. You may optionally
  add 1d6-3 to the final result to get the full range of possibilities.
  Optionally, you may use percentile dice for the attack roll also.
  Use the probability table in the back of the L5R rulebook. The
  probability for your Trait + Skill is your offensive bonus for that
  weapon.
  Defensive Bonus
  79
  
  To figure your DB, subtract fifteen from the TN to hit you. Do
  not count bonuses for armor (except shields), as that is included in
  the column the attack is rolled on.
  Concussion Hits
  Concussion hits are simply Earth multiplied by 16, plus 35.
  5.5 Werewolf: the Apocalypse™
  These conversion notes are provided mainly for Werewolf, the
  most combat intensive of the World of Darkness games. However,
  similar techniques can be used to convert other World of Darkness
  games.
  Note: Regeneration is commonly used by Werewolves, and will
  generally heal the effects of one critical strike or 15 concussion hits.
  You should keep track of aggravated damage and critical strikes
  separately.
  Armor Type
  Armor types for humans are easy to figure out, and will usually
  be Kevlar, None, or Soft Leather (Light). Glabro and Lupus forms
  give Animal (Light), while Crinos and Hispo forms give Animal
  (Heavy).
  Attack Type
  Most attack types for humans are obvious, because they use melee
  weapons or firearms. A Garou bite should be done with a maximum
  value of 120, while the claw attack would have a maximum result of
  150.
  Offensive Bonus
  OB is not used when converting from Werewolf. Instead, roll the
  attack normally. If you hit, that counts as a result of 75 on the attack
  table. For each success beyond the first, add 15 to that result.
  Note: This provides a limited number of results. You may
  optionally add 1d10-5 to the result for a wider range of possibilities.
  Defensive Bonus
  There is no defensive bonus. However, each success on Dodge
  removes 15 from the attack result. Soak does not apply, as the effect
  of Stamina on combat is figured into the concussion hits.
  80
  Concussion Hits
  A character’s concussion hits are 20 times their stamina, plus 25.
  Note that since stamina changes based on the Garou’s form, you
  should change the number of available hits also.
  5.6 Dice Pool Systems
  So long as your dice pool system uses an additive method of
  determining if one character can hit another, then using Arms Law
  is not difficult, and the critical charts can really spice up your game.
  By additive method, I mean that the player must add together the
  numbers on the dice and get equal to or greater than a certain
  number in order to hit a foe. If this is the case, then using Arms
  Law’s criticals can really enhance your game.
  The best method in this instance it to stay with the rules of the
  system to determine if your character hit or missed, and to just use
  the critical charts as supplemental damage.
  To determine if a strike does a critical, you must perform a little
  calculation. The first step is to determine the maximum possible
  result from the roll about to be made. You then subtract the target
  number from that maximum. Once you have this result, you divide
  it by 5 (rounding as needed) to give you a crit range.
  If the actual roll goes over the target number, determine how many
  crit ranges above the target number the result was, and this gives
  you the column on the critical chart to roll on to determine the
  critical.
  The results of a given critical would then be read and
  converted to the system as desired by the Game Master.
  Example: John is about to roll his attack for his character, Jinjin. Jinjin
  has a rating of 4d6+2 with his weapon. He has to roll a 16 or better to
  hit his foe. The maximum possible result for 4d6+2 is a 26. Subtracting
  the number needed to hit the foe from the maximum result gives us a
  10 (26 – 16 = 10). This result (10) divided by 5 gives a crit range of 2
  (10 / 5 =2). Thus a 16 is a hit, an 18-19 would result in an A critical,
  a 20-21 would result in a B critical, a 22-23 would result in a C critical,
  a 24-25 would result in a D critical, and a 26 would result in an E
  critical.
  
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  130
  Arms Law
  HEALING RECOVERY CHART
  This chart provides recovery times for most general inju-
  ries. When using it, apply the character’s Constitution bonus
  to any roll. The result is the recovery time for light injuries.
  Multiply the figure by 5 for medium injuries and by 10 for
  severe injuries. Halve the recovery time if the victim is
  hospitalized or placed in some other special care.
  TYPE OF DAMAGE (in days)
  Muscle/
  ROLL
  Burn
  Bone
  Tissue
  Head
  Organ Tendon
  01-15
  3
  5
  3
  10
  9
  7
  16-35
  2
  3
  2
  7
  6
  4
  36-65
  2
  2
  1
  5
  4
  3
  66-90
  1
  1
  1
  3
  3
  2
  91+
  1
  1
  1
  2
  2
  1
  5.9.2 • AD&D® Conversion
  Notes
  Because AD&D® is a role playing game that many people are
  familiar with, here are some conversion notes as an example of
  how Arms Law can be used with other FRP systems. To use Arms
  Law with AD&D® substitute the Arms Law attack tables for the
  AD&D® Hit & Damage Procedure.
  WEAPON SKILL
  To calculate the skill with a weapon that a character has
  proficiency in, use the following formula.
  OB = ([20 - THAC0] x 7) + Stat Bonus
  To determine the stat bonus for a given weapon, look up the
  most appropriate stat on the chart on the next page (use Strength
  for melee and thrown weapon, Dexterity for missile weapons).
  A character has a -25 (before stat modification) with a weapon
  with which he has no proficiency.
  LEVEL BONUSES
  Because levels are not the same in both systems, use the
  following for level bonuses.
  Warriors .............................................+5 per level
  Rogues ...............................................+2 per level
  Mages .................................................+0 per level
  Priests ..................................... +0 – +2 per level †
  † – depending on the nature of the diety—normal clerics
  would get a +3 per level
  � 5.9 �
  GM GUIDELINES
  5.9.1 • Healing Guidelines
  A GM should develop a comprehensive healing system for his
  world. This is a factor that controls how many and how often
  characters die permanently and how long they are out of commis-
  sion healing.
  HEALING SPELLS
  In a campaign game, the GM may want to make healing spells
  available in towns and cities. The GM should experiment with
  costs and requirements for healing services. This could range
  from spell users requiring only money for their services to spell
  users who will only heal “true believers” of their religion (or
  race). A complete set of healing spells is provided in Spell Law for
  healing by a variety of professions.
  HEALING HERBS
  One of the prime ingredients of a healing system is herbs
  (drugs). Herbs may be used to simulate the effects of certain spells
  in performing miraculous cures, are portable, and are usually
  much more available than high level healers. The GM can
  experiment with the numbers, prices and effects of whatever
  herbs he feels are necessary in his game. Below is an example
  some herbs found in one area of a fantasy would; other drugs
  might be available in other areas.
  NATURAL HEALING
  For the RM system concussion hits heal at a rate of 1 each hour
  if resting, and every 1 every 3 hours if active. The Healing
  Recovery Chart (below) gives the recovery time for a variety of
  injuries.
  EFFECTS OF INJURIES
  Another key factor in a healing system is the effect of the
  wound after being cured (by spells or herbs); some considerations
  in this area are: how long does it take to recover? should there be
  any permanent damage (often reflected in a lowering of stats)?
  what effect would the wound have on the character while he is
  recovering?  Most of these questions are very subjective and must
  be decided on a case to case basis. For example, having an arm cut
  off and then reattached might cause a loss of agility (temporary or
  permanent) and maybe a scar. Death and being raised from the
  dead might cause a general loss of abilities, partial loss of
  experience, and scars. Due to the variety of character systems
  which exist, these elements will not be detailed in Arms Law.
  Section 5
  GM Guidelines,
  Healing
  Guidelines,
  AD&D®
  Conversion
  Notes,
  Healing
  Recovery
  Chart
  SAMPLE  HERBS
  Name
  Home
  Form
  Prepare
  Apply
  Effect
  Abass
  Coastal Beaches
  Green Leaf
  Crush
  Eat
  Cure (2-12)
  Fiis
  High Altitude Lakes
  Tree Resin
  Dilute
  Drink
  Cure (1-5)
  Thurl
  Forests (comon)
  Brown Clove
  Brew
  Drink
  Cure (1-4)
  Mirenna
  Vales Above 10,000' (Rare)
  Silvery Berry
  —
  Chew
  Cure (10)
  Harfy
  Hilly Regions
  Scrub Resin
  Dry
  On Wound
  Stops Bleeding
  Ucason
  River Bands (Rare)
  Yellow Grass
  Burn
  Inhale
  Cures Blindness
  Jojojopo
  Base of Glaciers
  Grey Leaves
  Dry
  On wound
  Cures Frostbite
  Naza
  Plains
  Red Leaf
  —
  Chew
  Neutralize Poison
  Olvar
  Bay fo Glass Spires
  White Flower
  —
  Chew
  Lifekeeping (1 days)
  Kathkusa
  Nothern Icy Plains (Rare)
  Green Leaves
  —
  Chew
  2X Strength (2-5 rnds)
  Nelisse
  Volcano of the Udahir
  White Leaves
  Brew
  Drink
  Euphoria and Nutrition
  Agaath
  Mountains Above 20,000
  Blue Berry
  —
  Eat
  Breathe at High Altitudes
  
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  Arms Law
  131
  OFFENSIVE BONUS
  The remaining factors of OB are the same as presented in
  Section 5.5.
  INITIATIVE POINTS
  Convert Dexterity to a 1-100 stat using the chart below.
  DEFENSIVE BONUS
  Look up the character’s Dexterity on the chart below to
  determine the character’s Quickness bonus portion of DB. The
  rest of the factors in DB are the same as presented in Section 5.4.
  1-100
  3-18
  Stat
  Stat
  Stat
  Bonus
  102+
  20+
  +35
  101
  19
  +30
  100
  18
  +25
  98-99
  17
  +20
  95-97
  16
  +15
  90-94
  15
  +10
  75-89
  13-14
  +5
  25-74
  9-12
  +0
  10-24
  7-8
  -5
  5-9
  6
  -10
  3-4
  5
  -15
  2
  4
  -20
  1
  3
  -25
  HITS
  Arms Law is designed for a system in which a normal fighter
  will take just over 100 hits by 10th level. To accomodate for this,
  muliply the characters hits by 2 and add 10.
  GENERAL
  All other facets of the system remain as presented here.
  For conversion to any system, remember: the effectiveness,
  flexibility, and power of an attack is entirely contained within the
  offensive bonus of an attacker. So the offensive bonus should
  represent the potential of the attacker for inflicting damage.
  * AD&D® is TSR’s trademark for fantasy role playing products,
  and these references are in no way meant to indicate that ICE has
  a license from TSR with regard to this or any of our products.
  5.9.3 • Martial Arts
  Guidelines
  MARTIAL ARTS IN GENERAL
  In Arms Law, the martial arts rules have been designed to
  maximize playability while maintaining as many facets of real
  martial arts as possible. The Martial Arts Combat Summary Chart
  gives the combat capabilities of a sample of the martial arts
  existing in our world. Any other capabilities of martial artists are
  dependent upon the character system being used. Combat capa-
  bilities are described in terms of 2 attack tables and 2 critical
  tables devoted to martial arts. All normal Arms Law combat rules
  apply—unless they are specifically superceded by the guidelines
  provided in this section.
  THE MARTIAL ARTS “FORMS”
  The martial arts forms given are broad generic classifications
  and represent no specific style. The GM may modify any or all of
  the statistics given to simulate a specific martial art form. The
  forms given are primarily intended to provide an example of how
  the system can be used.
  We suggest that any player-character wishing to run a martial
  artist (warrior monk) be allowed to choose (or be assigned) one
  of the forms given. The fantasy character level values (experience
  or skill level) would determine the rate of progression of combat
  capabilities. Level capabilities that are not given can be easily
  extrapolated. It is suggested the non-trained characters be treated
  as novice boxers and novice wrestlers.
  Kung Fu is the source of most martial art forms (it has no belt
  system, but belts are included for comparison purposes). Kung Fu
  requires spiritual and mental training as well as physical training
  and thus the stats given are superior to the other forms (Kung Fu
  progresses equally in striking and sweeps and throws). It is
  suggested that characters wishing to be Kung Fu martial artists be
  given certain restrictions. Suggested restrictions include:
  1) a background (youth) spent in a religious order or retreat;
  2) a specific mission in life due to the background;
  3) personal enemies due to affiliation with the religion; and/or
  4) a very, very strict alignment of good (or evil).
  MARTIAL ARTS OBS
  The OBs given on the Martial Arts Combat Summary Chart
  include bonuses for expertise and level, but not for personal
  characteristics (strength, agility, etc.). A GM should examine the
  normal Arms Law offensive bonuses of his standard characters
  and compare them to the stats given. If there is a large difference,
  merely reduce the offensive bonuses given by 25-50%.
  INCREASED INITIATIVE POINTS
  Only martial artists may use part of their offensive bonus to
  increase their first strike points (see Section 5.6.1). For every 5
  points by which the martial artist decreases his offensive bonus,
  his initiative total is increased by 10 points. This reflects a martial
  artist’s capacity to focus his attack upon a very fast lethal blow.
  MULTIPLE ATTACKS AGAINST THE SAME FOE
  Certain Martial artists may make two attacks against the same
  foe in one round (if “Hasted,” a martial artist can make 4 attacks).
  Factor #1 following an OB on the Martial Arts Combat Summary
  Chart indicated the number of allowable attacks against the same
  foe. If this factors is not given for a given MA rank, the martial
  artist may not make multiple attacks against the same foe with that
  MA rank.
  To make multiple attacks, the martial artist must decrease his
  OB by 30, he must split his OB between attack and parry in the
  same manner for both attacks, and he must be using Martial Arts.
  Example:  Aurum (Black Belt, 3rd D., Japanese) has a
  +100 OB in MA Striking Rank 1 (“100 2/3/180˚ ”) and
  chooses to attack Edan twice in one round. Because he is
  striking twice in the same round, he subtracts 30 from the
  OB applied to each attack (i.e., he makes two +70 MA
  Striking Rank 2 attacks). Of course, he may use part of his
  OB to parry, and he still has the option of only attacking
  once at +100.
  ENGAGING MULTIPLE FOES
  Only martial artists can engage multiple foes in the same round
  of combat, without using special abilities or aid from spells (e.g.,
  “Haste”, etc.). Factors #2 and #3 following an OB on the Martial
  Arts Combat Summary Chart indicated the number of allowable
  foes and the maximum allowable angle of separation of these
  foes. If these factors are not given for a given MA rank, the martial
  artist may not engage multiple foes with that MA rank. To engage
  multiple foes, a martial artist must be using martial arts (unarmed
  combat) and he must subtract 20 from his OB for each foe
  engaged. He must also allocate his remaining OB between attack
  and parry in the same manner against all foes engaged.
  Example: Lauria (Black Belt, 2nd D., Korean) has a +80
  OB in MA Striking Rank 1 and is fighting two foes. He can
  attack one with his full +80 OB or both with a +60 OB
  against each (80 - 20). Since the chart indicates he can
  engage 2 foes within 180˚ (“80 1/2/180˚ ”), he can fight the
  two foes regardless of their angle of separation (e.g., even
  against one frontal and one rear attacker).
  Section 5
  Martial Arts
  Guidelines
  
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  132
  Arms Law
  INTERPRETING THE
  MARTIAL ARTS COMBAT SUMMARY CHART
  The example below shows how the combat statistics can be
  interpreted using the guidelines above and the key found at the
  bottom of the Martial Arts Combat Summary Chart.
  Example:  Consider a martial artist with a 3rd degree
  black belt in Japanese style karate. His DB of 60 applies
  to all foes that he is aware of. This example ignores
  weapon Kata.
  He could choose to fight using any one of his 8 rank
  abilities (4 striking, 4 sweeps and throws), or he could
  attempt to grapple with an offensive bonus (OB) of 50
  (maximum result on the Grapple attack table of Small).
  • With striking rank 4 and all four sweeps and throws ranks,
  he could only fight one target per round with the OB given.
  • However, with striking rank 3, he could:
  1) Fight 1 foe with a 70 OB, or
  2) Fight 2 foes (within a 90˚ arc) with a 50 (=70-20) OB
  against each.
  • With striking rank 2 he could:
  1) Fight 1 foe with an 85 OB, or
  2) Fight 2 foes with a 65 (=85-20) OB against each.
  • With striking rank 1 he could:
  1) Fight 1 foe with a 100 OB (1 attack), or
  2) Fight 1 foe with a 70 (=100-30) OB (2 attacks), or
  3) Fight 2 foes with an 80 (=100-20) OB (1 attack each), or
  4) Fight 3 foes with a 60 (=100-20-20) OB (1 attack each).
  EFFECT OF WEAPON KATA
  Certain martial artists use weapons as part of their Kata (kata
  are patterns of attack and defense that form the basis for the
  various forms of martial arts). Weapon kata may be used if a -20
  modification is made to the OB of the particular rank being used.
  Normal martial arts weapons include knives (daggers), jo sticks,
  nunchakus, tonfas, various swords, and other exotic weapons. A
  GM may wish to limit which types of weapons may be used and
  at which level of development in martial arts training their use
  should begin.
  It is suggested that knife kata be allowed at striking ranks with
  an offensive bonus (OB) of at least 50, and stick kata be allowed
  for sweeps and throws ranks with an OB of at least 50. It is further
  suggested that each martial artist be allowed to pick two other
  appropriate weapon kata that can be utilized by a rank that has an
  OB of 90 or more.
  A weapon kata attack is resolved in the following manner.
  1)  A normal attack is conducted on the appropriate martial arts
  attack table (striking or sweeps and throw). A OB modifica-
  tion of -20 is applied.
  2)  The weapon being used may be fumbled as specified in Section
  5.6.2-5.6.3. However, the fumble range is decreased by 1 for
  each increment of 10 that the OB is over 50 (round down and
  the range can never be reduced below 2).
  3)  The number of concussion hits indicated on the martial arts
  attack table is increased by: the difference between the maxi-
  mum number of hits the weapon can give [to the armor type
  (AT) being attacked] and the maximum number of hits that
  can be given to the AT being attacked by the martial arts attack
  table being used. The result is the actual number of concussion
  hits inflicted by the weapon kata.
  Kata Hits Delivered  =  normal MA hits +
  (Max Weap. Hits vs. that AT)  -  (Max MA Hits vs. that AT)
  Section 5
  Martial Arts
  Guidelines
  4)  In addition to the normal (if any) critical strike indicated by the
  martial arts attack table, a weapon kata also inflicts a second
  critical of one severity level less. For example, a result of C on
  the Martial Arts Strikes Attack Table would also inflict a B
  Slash (or Puncture) critical if a knife were used. Important:
  Only one die roll is made to resolve both criticals. The type of
  extra critical is always Unbalancing for sweeps and throw for
  weapons kata, while the extra critical type can be Slash,
  Puncture, or Krush for striking weapon kata. If more than one
  type of critical is appropriate for a given striking weapon kata,
  the attacker should choose which is to be applied—before the
  critical roll.
  Example:  Consider a martial artist with a rank 1 striking
  OB of 110. He decides to use a weapon kata utilizing a
  morning star against a foe with an armor type (AT) of
  9(-30). His OB is reduced to 90 (110-20) due to using a
  weapon kata (-20) found on Offensive Bonus Modification
  Chart). A morning star normally fumbles on 01-08; but his
  OB is 40 more than 50, so he would only fumble on an
  attack roll of 01-04.
  He makes an attack roll of 45, thus his net attack roll is
  45 (attack roll) + 90 (OB) – 30 (defender’s DB) = 105. If
  he had made a higher attack roll, it would not have
  changed the result because the maximum result for a rank
  1 attack is 105. The result from the martial arts striking
  attack table is “10B.”
  The maximum number of concussion hits that a morning
  star can inflict upon AT 9 is 27, the maximum for a MA
  striking attack against AT 9 is 19; so the actual number of
  concussion hits inflicted is 18 (=10+27-19).
  The critical damage is a 'B' martial arts Striking critical
  and an 'A' Krush critical are applied to the defender. Thus,
  if the martial artist rolled a critical result of 52; the 'B' MA
  Striking critical would stun the foe for 1 round and inflict
  6 concussion hits, while the 'A' Krush critical would force
  a parry at –25 for one round and inflict 5 more concussion
  hits.
  The grand total of damage would be: 29 (=18+6+5)
  hits, stunned one round, and forced to parry at –25 the next
  round (the worst damage inflicted is applied first).
  MA OFFENSIVE BONUS MODIFICATIONS
  (CUMULATIVE)
  –20 ........ For each foe over 1 engaged during a round.
  –30 ........ For using two attacks versus one foe in a round.
  –20 ........ For using a weapon kata.
  
SOURCE: textdata/thevault/Rolemaster/Utilities/RM Arms Law Conversions to D&D3_5,AD&D,GURPS,etc.pdf