Mandagor

Concept: “Black or nebulous forms, they gaze upon mortals with piercing red eyes filled with mischief and wickedness.”
Content: An multiform creature and potential companion to generous scvm
Writing: Provides copious lore pertaining to behavior and ecology alongside stat blocks for various forms
Art/design: Predominantly textual, leveraging color to differentiate certain blocks; includes some cleverly placed depictions
Usability: Contains a fair number of behavioral details for GMs to keep track of