Animancers, necromancers, and other unscrupulous spellcasters who experiment with the bodies of kith have been known to create all sorts of constructs and vessels. Some exist as subjects for study, and others are sources of amusement.
Void seers are skulls filled with essence. The first accounts of void seers come from Old Vailia, where a now-infamous necromancer created them as a diversion for court. Since then, they've been used as patrols, guards, and attendants. Their small size makes them easier to create and direct.
Encountered in wizard domains, primarily Crägholdt, the skulls are poor fighters, but decent casters. Smack them out of the air.