The deadels are undead creatures created by K'Z'K. Seemingly at will, K'Z'K can turn dead bodies into these creatures, immediately turning them into monstrous mockeries of their former selves, with glowing yellow eyes, sharp teeth and bad skin. Deadels aren't much more powerful than humans except that they're much more difficult to kill, though blowing one's head off is generally enough. Deadels sometimes speak like intelligent if rather weird creatures, and at others mindlessly repeat the name of the target they've been assigned to kill. Some servants of K'Z'K look otherwise like deadels but have extra features such as wings.
K'Z'K has been shown to raise deadels in a large area by letting out a call inaudible to humans, and during the War of the Bug Squishers, it seemed anyone who died in Mercia or Trent could turn into a deadel, their souls stolen by K'Z'K in the process. They formed the bulk of his army at that time.