Ice Shard

Summons an Ice Revenant. The Ice Revenant lasts 180 seconds.

Source
Kael and Lady Vashj can find one in The Crossing, the secret level of the Frozen Throne alliance campaign, Curse of the Blood Elves.

In the RPG
This item looks like a chunk of ice carved from the purest crystal. When held, it seems to draw body heat from its owner, chilling his flesh in a notable, but harmless, manner. When activated, the shard transforms into a frost revenant with its weapons ready. The creature obeys as long as it is not given orders contrary to its nature, such as to work alongside a fire revenant, attack other frost-based creatures, and the like. Should these conditions not be met, or if the summoner is slain, the frost revenant goes rogue immediately and acts as it sees fit, either fighting if it feels victory is assured or fleeing to make its own way in the world. If the frost revenant is slain, or a full hour passes, it reverts to statuette form. Should this figurine come in contact with an inferno stone, both objects explode.