Hrimthurs: the Hammer of Forever (Hrim-thirs)

In the mythos of Filfier and Giants, an Ice Giant existed: Hrimthurs. He was an untamed menace, known for his unending rage and inability to tell friend from foe, he slain many people with no purpose. Eventually calming down, he instead secluded himself to mountains, alone. Whether he died in combat or not is unknown, but his ice hammer has been brought into the mortal realm, and has been claimed by Lefnar since it came. 
The hammer is made of an ice that never melts, reflective of it status as an item from another realm. It can cause frostbite, quickly freezing over limbs it hits. It can also be slammed into the ground to make shockwaves, shooting a cold breeze that could push even giants off balance.