Julius of the Fell was a mortal man, near the lands of morder and his late father who had been a hermit along the southern most edges of Mordor. After the destruction of the ring and the collapse of Mordor, Julius stumbled upon several hatchlings of fellbeasts who were to have been bred for Sauron' armies. Over the next four years the creatures grew fast in his care and he fed them fresh wholesome meats and despite their continued black color they grew to fearsome creatures very different from their orginial breeding. Under his care he bred them like one would breed dogs for hunting. And when they were fully grown they were bound to his will.
Burning his cabin he fled with his beasts to farmost eastern lands where he continued to breed his fell beasts till their numbers were in the hundreds, confronted by soldiers of the searaiders he fled further with his beasts to Utumno. Over the course of 20 years he bred his fell beasts with the last of the dragons to create beasts who bore little resemblence to what they had once been, and using them now with dragon fire in their bellies he used them to scorch the entire lands of Utumno till nothing lived down to deepest and darkest pits of the land. Cappturing what remained of the goblins in those moutains he forced them to construct 12 rings in the land each 1000 meters deeper than the last and in these rings fires burned to keep his beasts warm and to cook both goblin and man to feed his massive army of fallen wyrms.
For hundreds of years they would raid and terrorize middle earth devouring entire villiages at times only within 700 years time was man strong enough to again be able to wage war. Together they gathered a force of both dwarves and man (for elves were no longer around) and they gathered to destroy the outlying breeding grounds of the fallen beasts.
Julius upon feeling their deaths aged rapidly and became mere skin upon bone, wraith like and vicious, realizing that his life force was tied to his beasts he bred, he tripled their breeding speeds to reinforce his lifeline.
Nearly 1266 years following the destruction of the ring, after luring the beasts out of Utumno, the Armies of men slaughtered all the remaining fallen beasts.
And when the last beast was killed, in screech which shook the very mountains surrounding Utumno Julius perished in violent explosion which caused the 12 rings which foundations were stable so long as he lived, thus too collapsed and all that could be seen for a hundred years more was a thick black smoke rising from where the the rings had once been.
At last all the last beasts of evil from the time of Morgoth and Sauron and now Julius, were dead, and gone.