Cthulumon is the Mega Level form of Shoggothmon, and an Evil God type Digimon from the Dark Area. It is a gigantic Digimon, and is thought to be as old as the Digital World itself. He is worshipped by Migomon and Nyarlathomon, and has the ability to drive anyone who looks directly into its eyes mad.
Cthulhumon stands higher than a ten-story building, with scaly yet slimy skin a blend of yellow-green and brown. Its head is like a giant octopus attached to its neck, with many prehensile tentacles hanging from its "chin". Its body is vaguely humanoid, but also quite draconic, with great bat-like wings and feet with many tentacles acting as toes.
- Call of Cthulhumon - Cries out with a forbidden language to gather its followers and then drive them mad
- Tentacle Stomp - Stomps on the foe with its tentacle tipped feet
- Curse of Cthulhumon - Infects the data of the foe with an ancient virus that slowly corrupts their data
- Cosmic Terrors - Unleashes horrors from across the universe upon the foe