The Skeleton of One-Eyed Giant is an NPC found in Necron's Coliseum, in the bottom area, right after a lake of lava.
"Skeleton of One-Eyed Giant made by the best Mage on the northern continent, Shaddam. Shaddam only could become the Mage who owns the Coliseum because of this Giant" - Truth Mirror description.
He is a giant black skeleton, who talks to you briefly and subsequently disappear, leaving the Psycpros Collar.
"This useless war must end. This is not what my Master Shaddam had wanted. In wars, many things are lost, and nothing is gained by fighting. The only thing that remains is Shaddam's great power. Accept his energy and powers."