A Hellish Alliance was a phrase used to refer to people who sided with dark forces in the Deryllium Universe.
- Rusultru was said to have had a Hellish Alliance with Death.
- Ronok was corrupted over time and became an advocate of evil. However, some of his Aspects tried to stop him.
- You-Know-Who was said to have been in a Hellish Alliance, however this was show to be false.
- The Editor may have entered a Hellish Alliance when he created the Dark Horde.
While never seen in any sources, the phrase referred to Hell, a word used to describe a terrible place of suffering. However, it could simply mean extremely difficult or unpleasant and not actually refer to any demonic entities.