Dæmons

Publisher's blurb:

The concept behind these dæmons is that they come from a realm outside of space and time (astral plane, the Outer Dark, the Void, primordial chaos, ...) and lack any true physical form. When encountered, it's either through astral travel to their native realm, or they are possessing a physical body in the material world. A short duration summoning spell can create a temporary magical body that mirrors the dæmons astral form, but these immediately dissolve when the spell ends or the dæmon is slain (and returns to it's realm).