Ouija were once mages, only they have been demonically corrupted and transformed by the Genma to serve them and use thier magics for other purposes for all eternity.
They don't have a true physical form but rather appear as a spirit that floats in the air. The lower section of thier bodies have been cut off and replaced by an arcane magic, which they use to power thier magics and rely on to move freely where they please. the Ouija's lower face is also covered by a mysterious viel that hides thier identity, but two glowing eyes can be seen at the top of this.
The only real way to hurt one is to shoot them with arrows. If you manage to knock one out of flight, quickly switch to physical attacks, as it can finish them off in no time. Watch out for it's magic reel attack, which can trap the player and can either drain health, magic, or even red souls. Some thier reels can also inflict elemental damage. If you find yourself swarmed with other Genma, then it's a good idea to finish this demon off first as it's reels can become a nuisance while fighting other Genma.