While in the Realm of the Underworld Prince Algor fought a great many Archfiends in battle, but only one of them managed to take a bite out of the Prince. After being run through with a sword and left to die the Rip Sludge that makes up all Slimes began to work it magic on the Skeletal form. Awaking full of power the Fiend discovered a deep need to ingest more of Algor. Taking the shape of his true desire, and roaming the Underworld searching for more of the slime he craves he was found by the Acromancer who used his magic to send this Fiend through a portal to Jalldoon (which the Acromancer had opened after the Prince had escaped his evil spell) to hunt down the turncoat Slime.
Appearing on Jalldoon the Slime Fiend wandered through a dark forest until he happened across a traveling party of Slime merchants. Seizing upon them the Slime Fiend feasted until he was satiated, and this was when he found that ANY Slime would calm the gnawing hunger inside of him. The Slime Fiend has been imbued with the magic of Slimes, and while not capable of full shape shifting he can turn into a black puddle of sludge to pass through almost any size opening. Haunting the Jalldoon night looking for more Slimes to eat the Fiend cracks open any slime he comes across with his mighty hammer. The citizens of Slime City have yet another reason to cower in fear when the Jalldoonian Sun sets . While the Slime Fiend will eat whatever Slime he sees to settle his wants he still hunts his original prey, woe to Prince Algor when he and the Slime Fiend cross paths again.