The Plate of the Damned is massive in form and covered with layers of arcane etchings, yet this imposing armor rests lightly upon the wearer. It was crafted by demons, along with the Helm of Domination, and given to Ner'zhul to make him nearly invulnerable. Along with the Helm, the armor was bonded to Ner'zhul's spirit and locked within the Frozen Throne. It is currently unknown where the Plate of the Damned is since its former wearer, Arthas Menethil, is dead.
Arthas did not appear to use the armor in Northrend, instead using what looked like death knight armor as the Lich King.