Ice Spirit is one of the new cards that was added to the game on the 4th of July patch update. It can be obtained in the new 2300+ trophy arena called, Frozen Peak. There are currently only 3 cards there and Ice Spirit is the solo common card that you can get.
Ice Spirit works similar to Fire Spirits. They jump in to their target to deal damage and get killed on the process. But there are differences with the Ice Spirit and the Fire Spirits. First, Ice Spirit is only a single troop that freezes its target for 2 seconds. Second, it only costs 1 elixir, making it the second cheapest card in the game aside from the Skeletons.