TEXT: The Nine Hells and their Lords
  Layer Name
  Ruler
  1.
  Avernus (bloated wasteland, few structures and ruins)
  Zariel (impatient, temperamental, fallen angel)
  2.
  Dis (sprawling metropolis, mines, workshops)
  Dispater (paranoid, curious, loves secrets)
  3.
  Minauros (wretched swamp, cheap and flimsy buildings)
  Mammon (greedy, miserly)
  4.
  Phlegethos (volcanoes, taverns, theaters, casinos)
  Belial (master planner) and Fierna (manipulator)
  5.
  Stygia (frozen sea, perpetual warzone)
  Levistus (imprisoned, master soul tradesman)
  6.
  Malbolge (prison, large, steep mountain, avalanches)
  Glasya (unpredictable, rebellious, criminal)
  7.
  Maladomini (war-torn wasteland, archives underground)
  Baalzebul (manipulator, liar)
  8.
  Cania (glaciers, ice storms, arcane experiments)
  Mephistopheles (arcanist, intellectual, researcher)
  9.
  Nessus (empty, rocky wasteland)
  Asmodeus (cunning, persuasive, strategic)
  Avernus Cheatsheet
  Hideous clouds that obscure the sky
  Frequent meteors crashing into the ground
  Bone �ields, quicksand, tar pits, lakes of lava, salt �lats
  Ambient light from just below the horizon
  Reeks of brimstone and burning tar
  Hot gusts of wind scour the land
  Charting a Course
  Distances and travel times are always changing.
  When a character wants to go somewhere on the map,
  they roll two dice depending on the situation:
  New destination (2d4)
  Already visited destination (2d8)
  Led by a native guide (2d10)
  If the two dice match, the characters get to other location.
  River Styx
  If in or drinking from river, feeblemind spell (save DC 20).
  Water from River Styx loses potency after 24 hours.
  Telepathic Communications
  In the Nine Hells, Archdevils can eavesdrop on message,
  sending sending	stones, helm	 of	 telepathy, serpentine	 owl,
  orb	of	dragonkind and so on.
  Demon Ichor
  Demon ichor forms pools and small lakes.
  If a creature comes in contact with Demon Ichor, DC 10
  Con save (�iends, oozes, plants and undead are immune).
  On failure, roll on Flesh Warping table (BG:DiA p. 78)
  Food and Drink
  Wisdom (Survival) checks with disadvantage.
  Water and food tastes foul, even if brought from outside.
  Optional Rules
  Bargains. If a creature fails a death save, archdevil may
  offer assistance in return for unnamed task. If character
  agrees, automatic 20 on next death save. Character falls
  under geas spell (no saving throw allowed).
  Exhaustion. Non-evil creatures must make Con saving
  throw after every 1 hour of travel. DC 10 + 1/hours
  traveled. On failure, one level of exhaustion.
  Pervasive	Evil. At the end of long rest, non-evil creature
  must make DC 10 Wis saving throw. On failure, alignment
  changes to lawful evil. Permanent if creature doesn't leave
  within 1d4 days. Dispel	evil	and	good reverts aligmment.
  Infernal Hierarchy
  Devil
  CR
  Source
  Least
  Lemure
  0
  MM p. 76
  Nupperibo
  1/2 MToF p. 168
  Lesser Devils
  Imp
  1
  MM p. 76
  Spined Devil
  2
  MM p. 78
  Bearded Devil
  3
  MM p. 70
  Merregon
  4
  MToF p. 166
  Barbed Devil
  5
  MM p. 70
  Chain Devil
  8
  MM p. 72
  Bone Devil
  9
  MM p. 71
  Greater Devils
  Orthon
  10
  ToF p. 169
  Horned Devil
  11
  MM p. 74
  Erinyes
  12
  MM p. 73
  Narzugon
  13
  ToF p. 167
  Ice Devil
  14
  MM p. 75
  Amnizu
  18
  ToF p. 164
  Pit Fiend
  20
  MM p. 77
  Warlords of Avernus
  Raggadragga (a wereboar with 2 wereboars, 2
  wererats on a Demon	Grinder)
  Bitter Breath (a horned	 devil with 3 hobgoblins in a
  Tormentor, a hobgoblin	 warlord on a Devil's	 Ride, 2
  hobgoblin	 captains and 14 hobgoblins on 2
  Scavengers)
  Feonor (an archmage with a ghast, 6 ghouls and 10
  crawling	claws on a Demon	Grinder, and 8 mezzoloths
  on 2 Tormentors)
  Princeps Kovik (a chain	 devil on a Devil's	 Ride with 2
  bearded	devils also on Deviæ's	Rides, 4 barbed	devils
  on a Tormentor and 8 bearded	 devils on a Demon
  Grinder.
  
SOURCE: textdata/thevault/Dungeons & Dragons [multi]/Adventures/Eventyr/Complete DM's Bundle - Baldur's Gate - Descent into Avernus/Avernus Cheatsheet.pdf