From publisher blurb:
The materials presented in this booklet are optional, providing additional monsters as challenges to player characters.
These rules provide a method to generate Fiends – Demons and Devils – for parties of Shadowdark adventurers to encounter.
These Fiends range from Level 1 to Level 30, and gain ever greater power as they advance.
The system can also be used to create Fiendish characters, as “Ancestry Classes,” should a group desire to explore adventures in the Underworld using ancestries native to the region.
Designed for use with Shadowdark, easily adaptable to any other classic style OSR Role-Playing Game.
Liber Diaboli – The Book of Fiends includes:
Cosmology and The Damned
Discourse on Demons & Devils and Other Denizens of the Underworld
Summon Fiend Spells
Ilks – “Ancestry Classes” of the Underworld
Fiendish Ranks
Fiendish Level Advancement
Abilities & Talents Details, including:
Elemental Attacks
Impervious Details
Multiform Ability
Fiendish Power
Size
Spellcasting Ability
Summoning Ability
Optional Possession Rules
D66 Chaos Talents
D666 Unusual Trait Table
Catalogue of 24 Fiendish Ilks includes:
Buzzing Fiends (Fly, Stingbat, Stirge)
Clattering Fiends (Bone, Skull)
Corrupting Fiends (Imp, Quasit)
Crawling Fiends (Centipede. Scorpion, Spider)
Croaking Fiends (Frog, Hezrou, Toad)
Freezing Fiends (Frost, Ice, Snow)
Gibbering Fiends (Ape, Baboon, Monkey)
Goring Fiends (Malebranche, Minotaur)
Groaning Fiends (Nalfeshnee)
Grunting Fiends (Boar, Orc, Pig, Swine)
Gutting Fiends (Barbed, Spined)
Hissing Fiends (Marilith, She-Devil)
Howling Fiends (Bear, Glabrezu, Wolf)
Moaning Fiends (Lemure, Nupperibo)
Oozing Fiends (Mold, Ooze, Slime)
Raging Fiends (Bearded, Dwarf)
Ravaging Fiends (Dragon, Wyrm)
Roaring Fiends (Balor, Pit)
Scorching Fiends (Fire, Lava, Magma)
Screeching Fiends (Vrock, Vulture)
Slinking Fiends (Shadow, Skulking)
Slithering Fiends (Serpent, Snake)
Weeping Fiends (Dretch, Manes)
Whispering Fiends (Incubi/Succubi)
Larvae