From the introduction: Phantasmos [is] a d20 supplement that explores the nature of dreams and the mysterious plane given form by their phantasmal energy. The supplement is intended for players and GMs alike, and includes many new spells, prestige classes, and character options along with new creatures, story ideas, and full information on Somneiros, the dream plane. User summary: Several "web enhancements" were made available for this sourcebook.