According to Human Demonologists, he ruled over twenty legions of demons under his command, and he "taught all wonderful sciences, being an excellent poet, and was to be very obedient to the conjurer. Phenix hoped to return to Heaven after 1,200 years, but he was deceived in this hope."
His preferred form was of a phoenix.
He fought during the Car'Haadhook war. He clashed with the command of Pukunta, and felt like the Car'Haad could have been allies instead, and his body was slain during the Siege of the Sky Halls -some said, either to Pukunta or one of her minions. But the Phoenix did raise again.
His forces had been depleted during the Car'Haadhook war, and only played a minor role during the First War of the Power, and was in the process of rebuilding it when he was called to reinforce the legions in what will be the Battle of Montes Cado. Slain again, the Phoenix did raise again, to fight -and be slain, and rise again- in the Battle of Polforia.
He will be captured at the end of the Siege of Dol-Nur, and the elves will bring Phenix the Phoenix to the Order of the Watchers of Hellsgate. Unable to destroy the body that kept returning to life and take out his soulstone, for so powerful had been the art of Phenix, they put him under a lava cascade, to keep his vessel being burned over and over, and so trap his soulstone.
But when Hellsgate was broken and the Soulstones liberated, Satman decided to keep Phenix on this torture, as Hellsgate came to be under his rule: and wouldn't be until the fall of Satman, that Phenix was broken of his chains and went flying again to the skies of Aiers: but he wouldn't return to the Dark Legions... and some said, he even fly far, far away, to Dahl'Haran, to teach the enemies of Demons.