Mortos der Soulstealer is a demon warlock from the "spooky realm" who is released every thousand years when Taoola and Charcunga are aligned. He is obligated to grant one human a wish every thousand years before returning to his dimension, and was befriended by Dib for this reason. However, Mortos claimed that in order to use his catastrophic powers, he must recharge by ridiculous means.

These include hugging puppies, consuming huge quantities of food from MacMeaties and clothes shopping.

Although Dib intended to use Mortos to steal Zim's soul, the plan backfired when a passerby wished for ice cream. Mortos granted his wish, and departed to the spooky realm. The ice cream was discarded upon the revelation that it contained raisins.

Before he became evil, he used to have a friend who sang to him, but broke his heart. Dib also described Mortos as being a mooch, since he had to pay for all of Mortos' "recharging."

He seems to enjoy the feel of tombstones on his face, and wears boxer shorts with hearts on them . He also hates the "Ancient Pamphlet" that binds him to wish-granting. His only friends are the dark energy of the universe and a girl named Darlene.

The only episode that Mortos der Soulstealer appeared in or was mentioned is Mortos der Soulstealer.

Characters of Invader Zim
Main Characters
Dib • Gaz • GIR • Zim
Supporting Characters
Almighty Tallest Purple • Almighty Tallest Red • Ms. Bitters • Professor Membrane
Minor Characters
Invader Skoodge • Keef • Minimoose • Tak • President Man • Roboparents • Lard Nar • Skool Principal
Background Characters
Adult Dib • Old Kid • Hobo • Alan • Meef • Skoolchildren
Temporary Characters
Mortos der Soulstealer • Sergeant Slab Rankle • Sergeant Hobo 678 • Shadow Hog • Chickenfoot • Sizz-Lorr • Gashloog • Willy • Iggins • Walton Chunky • Pigboy
Canceled Characters
Louie • Digestor • Almighty Tallest Spork • Almighty Tallest Miyuki • Bloody GIR • Cthulu • Cybernetic Kitten • Dinky • Little Timmy