The Úvanimor were monsters of various kinds created by Melkor (Morgoth). They appear in several of J.R.R. Tolkien's earliest tales included in The Book of Lost Tales and The Lost Road and Other Writings.
While in the North, Morgoth built his strength and gathered his demons around him, the Balrogs. There he made the Úvanimor, monsters of diverse kinds and shapes breed from the earth; they were monsters, giants, ogres and Wicked dwarves (the Nauglath) and these were the agents of Melkor - but Orcs were not made until he had looked upon the Elves.
Úvanimor feared the sinews of Tulkas' arm and his iron-clad fists, when he had cause for wrath.