It’s no accident that so many evil wizards and especially sorcerers are portrayed wearing masks. In many cases, the mask is more than just a carved object—it is the home of an evil spirit oni.
Without physical bodies of their own, oni’s forms tend to be twisted emulations of mortal creatures. As the weakest and most cowardly oni, spirit oni don't even have the fortitude to manifest a bad physical copy; instead they inhabit masks specially prepared for them. But—bitter, resentful creatures that they are—they immediately regret this lesser form, making them difficult servants who look to trade up to more powerful masters.
Spirit oni are a great way to give enemy low-level spellcasters a bit more magical and melee oomph (“That sorcerer you tied up? His mask is alive and chewed him free. And it bit your sorcerer on the way out for Charisma damage.”), and to further set them apart as having participated in rituals no PC would dare. And since every culture and time period has masks, spirit oni can fit into almost any campaign. Or if you’re feeling thematic, they might team up with other floating head monsters, including vargouilles, beheaded, sagaris, and penanggalens.
Blind Joppa is the only witness to a murder, and the tapestry of sounds and smells he reported to authorities leads only to conflicting dead ends. Actually Blind Joppa himself is the murderer. The blood sorcerer can see perfectly fine through his spirit oni familiar’s eyes, and his story is an out-and-out falsehood with his blindness being the perfect alibi.
The High Street Harlequins are a louche band of bards and players given to absinthe and spreading rumors of their own devil worship. But the head Harlequin, the Masked Butler, is no actor—he really is a diabolist who specializea in capturing minor (size Small or smaller) fiendish creatures. His personal effects are guarded by a rack of spirit oni disguised as commedia dell’arte masks.
There is a willow tree outside of town that is avoided by all the locals. There masks said to be the death masks of evil men flit about the boughs like birds. The masks are free-willed spirit oni tired of serving mortal masters but too afraid to pay the high cost of reincarnation. Usually they prey on lone travelers, but they occasionally will cast commune if they are allowed to lap at fine rice wine or an open wound or sore.
—Pathfinder Bestiary 3 209
Edit: Thanks for your patience. The day this entry was supposed to go up was rather busy. Original post:
At least I have a good excuse—not only am I on Hour 14 (and counting) of my workday today, but there’s a music video being filmed outside my office. And I mean right outside my office.
Speaking of which…do you have a band? Do you like Walk off the Earth or John Legend? Do you want to perform with them? You might want to click here.