Glacial Spike (dagger)

Source
Glacial Spike is a quest reward from the mage-only quest Destroy Morphaz which starts with Archmage Xylem in Azshara.

Trivia
Glacial Spike is a removed item that used to be a reward from the Sunken Temple mage class quest. The Diablo II version had a proc that caused an AoE explosion and froze enemies in place--the WoW version had Frosty Zap, a chance to restore mana when casting Frostbolt.