Aseroth

Aseroth, called the Winter Warlock, was a demon lord associated with ice and cold.

Realm
Aseroth ruled the 566 layer of the Abyss, a vast realm of glacial ice and snow called Soulfreeze. So bitterly cold and malevolent was Soulfreeze, that a creature's thoughts and emotions could be frozen and drawn out of their heart and mind to drift on the wind as ice crystals. Aseroth ruled his realm from a deep fissure in the ice sheet called the Crystal Caverns. Demons, remorhazes, and ice archons all lived and served there.

He also had an iron fortress where he left his body while astrally traveling. The fortress contained no treasures and was guarded by 10 mariliths who simply warned possible intruders to go away. If the fortress was attacked, however, Aseroth would return to his physical form immediately.

There was a portal between Soulfreeze and the Para-Elemental Plane of Ice.

History
Aseroth was said to have once been an elemental prince of evil who became a demon lord.