TEXT: Four Against Darkness
  V1.1
  Final Boss table (d6)
  A final boss always fights to the death, and never tests morale, so there
  is no reaction given in the descriptions below.
  A final boss cannot be met as a wandering monster.
  1
  Mummy. Level 5 undead, 5 life points, 3 attacks, 1 treasure roll at +2. Any
  character killed by a Mummy becomes another Mummy and must be
  fought by the party. Mummies are attacked at +2 by the Fireball spell, but
  are immune to the Sleep spell. If each character is already being attacked
  once, extra attacks are against a Cleric if there is one in the party. Clerics
  add their level when attacking a Mummy.
  2
  Orc Brute. Level 5, 6 life points, 3 attacks, 1 treasure roll at +1 but may not
  have any magic items, treat as 2d6 x d6 gold pieces instead. If each
  character is already being attacked once, extra attacks are against an Elf if
  there is one in the party. Elves attack and cast spells against the Orc at +1.
  3
  Ogre. Level 5, 7 life points, 2 attacks, 1 treasure roll. Each hit from an ogre
  inflicts 2 life points of damage. Dwarves add +1 on their Defense rolls, and
  Halflings add their level to Defense rolls when facing an Ogre.
  4
  Medusa. Level 4, 5 life points, 2 attacks, 1 treasure roll at +1. All characters
  at the beginning of the battle must save vs a level 4 gaze attack once or be
  turned to stone. Petrified characters are out of the game until a Blessing
  spell is cast on them. Rogues add half their level to this save.
  5
  Chaos Lord. Level 6, 5 life points, 4 attacks, 2 treasure rolls at +1. Before
  the fight begins, roll d6 to determine of the Chaos Lord has any special
  powers: 1-3 no powers, 4 evil eye (at the beginning of the battle all
  characters must roll 4+ or be at -1 on all defense rolls until the Chaos Lord
  is slain), 5 energy drain (any character taking a wound from the chaos lord
  must immediately  roll 4+ or lose 1 level), 6 hellfire blast (before combat,
  all characters must roll 6+ or lose 2 life points; Clerics add ½ level to this
  roll). When you kill a Chaos Lord, roll a die; on a 5-6 a character of your
  choice finds a clue (see p.58).
  6
  Small Dragon. Level 6, 6 life points, attacks: see below, 3 treasure rolls at
  +1. On each turn of the Dragon, roll d6 to determine what it does. On a 1-2
  the Dragon breathes fire, inflicting 1 life to all characters who fail to save
  vs level 6 dragon breath (each character adds ½ level, rounded down). On
  a 3-6, the Dragon does not breathe, but bites/claws 3 random characters
  instead. Dragons are are immune to Fireball and Sleep spells. Gain a bonus
  2nd XP roll if the Dragon is slain.
  The gold piece treasure (the sum of rolls of 1-2 on the treasure table) of a final
  boss is tripled, or increased to 100 gp, whichever is best for you. If it has a magic
  item in its treasure (a roll of 3 or 6+ on the treasure table), you will find two
  magic items instead.
  
SOURCE: textdata/thevault/Four Against Darkness (osr)/Sheets and Play Aids/Four Against Darkness Final Boss Table ( v1.1).pdf