Izh'kafel was a necromancer, like Sauron, and was also taught by Morgoth. He is known to be Sauron's rival during the early days, though not as powerful as Sauron. He has been known since as Izh'kafel the Frosted.
He was once a follower of Morgoth, but only a few know this, for he fled from Morgoth like a coward before the War of the Jewels happened. He established a kingdom in secret far to the south, no one knows of it. He practised dark magic in secret and so as a result, he learned to create the Undead, which composes the most part of his armies. Before Morgoth was defeated, he cursed Izh'kafel, who left him in his time of need. And so the kingdom of Izh'kafel was lain waste, frozen by ice, his power vanished, with Morgoth's fall. He was sealed within his great tower, but his power was not ceased, and he still has some loyal followers, which will obey him not matter what.He was also aware of Sauron's fall, and planned to take the North as soon as his curse was no more. He knows that the only way for him to get out of his tower and regain power was to regain his blade, Frostmourne, which was lost to him in an unknown way. However, Sakos Flamefist has kept the blade after finding it and has made multiple enchantments to prevent Izh'kafel from holding it or even letting it near himself without feeling an unbearable, agonising burning within his body.