The Icebrand will summon 3 ice crystals, which will deal damage based on your INT. They will go through walls, and lasts about 30 seconds. This is the same effect that the FrostShard has, with the added bonus of dealing large melee damage, albeit with a long swing speed. It will give you a +10 INT bonus while wielding it.
Simply swinging the Icebrand does not decrease its durability as well as hitting something with the beam. Durability will only go down after hitting an enemy.