Lucifuge is a corrupted dark angel sealed within the Doomsayer's Island. A thousand years ago he served Haeresias, the last king of the Moon Elves of Mercution, and became entombed when the wizard-priests of Ennon sunk the kingdom under the Crystalline Sea. Despite of this, his presence seeped through the soil in one of the smallest Free Islands, which became known as Angel Island. For a long time, the island was a center of witchcraft, and werefolk and vampires also sought refuge there. This changed when the Doomsayer, one of the Veterans of Heroica, moved to the island and accidentally released Lucifuge. The wizard dwarf and the dark angel duelled, and in the end Lucifuge was sealed in crystal while the dwarf lost his mind.
250 years later, a group of heroes from Heroica went on a mission to investigate the island, and they came upon the crystal that held Lucifuge. They caused a crack on the crystal, allowing the dark angel to reach out to them and turn them into Nephilim, his obedient servants. His order was for them to return to their organization and destroy it from within in his name. However, the Nephilim were discovered and slain, and the Doomsayer's Island was declared forbidden to enter.
Lucifuge remains within the crystal seal, waiting for another chance to exact vengeance upon Heroica.