Rituals and Spell Objectives and Design I.
Peter Carroll
Legend Core Rulebook
Unknown
Call of Cthulhu
The New Orleans Guidebook
CoC
Wolff King Morrow
Planar Handbook
Bruce R. Cordell & Gwendolyn F.M. Kestrel
Book of Challenges: Dungeon Rooms, Puzzles, and Traps
Daniel Kaufman