They take the form of floating human-shaped skulls that radiate a green glow from their eyes and mouths. Their portrayed size varies greatly; in the OVA they are roughly human-sized, but in the 2012 anime they are as large as buildings. In the Innocent Soul manga, however, they can seemingly change their size at will.
In the OVA, the Skulls were only seen using one method of attack: ramming. Although inelegant, their charges are fast and considerably forceful.
In the anime however, they can bond together and create a humanoid figure out of the corpses of Dead Master's minions.
- In the manga series, Dead always refers to them as "Skull-Chan".