Izh'kafel was a necromancer who was taught in the dark ways of sorcery by Sauron. He grew threacherous however and began making plans to establish himself as a dark lord, however his betrayal was discovered and he was forced to flee his former master's wrath.
He was initially a follower of Sauron, but only a few know this, for he quickly came to covet the secrets of his Master's strength. Melkor, who was a known traitor to both sides, hoped for mercy from the Dark Lord and became a servant of his will. Seeking to appear loyal, the fallen Vala began spying on Izh'kafel and learned of his plans. He revealed what he knew to the One, who was angered by this and ordered his lieutenant, Kosomot to bring the Maia to him in chains. Fearing Sauron's wrath, the necromancer fled Angband.
He established a kingdom 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 Sauron was defeated in the War of Wrath, 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. 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.