Doomion is a demon encountered during the Underground Pass Quest, and can only be fought during the quest. When killed he drops the Amulet of Doomion, which is needed to obtain Iban's shadow. Protect from Melee should be used during this part of the quest to save life points for coping with its attacks. It is possible to use the small bridges connecting the platforms as a safe spot to attack using Ranged, Magic, or with a halberd. In the quest, the player must also kill the other demons, Othainian and Holthion.
His name seems to be a portmanteau of "Doom" and "Minion".
Doomion, along with Holthion and Othainian, are the lowest level demons to drop infernal ashes. However, they are very far from any bank.
- On release, Doomion was a black demon unlike the other demons. This was later changed and Doomion was made consistent with the rest.