A Deer Antler is an Item exclusive to Don't Starve Together, introduced in A New Reign. It is dropped by the antler-type No-Eyed Deer after charging at objects such as Trees. Trying to use a Deer Antler to unlock the Loot Stash will destroy the antler, drop a Bone Shard and cause Klaus to spawn. There are three visual variants of the Deer Antler, that all function in the same way. The antler serves no other purpose than being used on the stash.
With a way to ward off Klaus that spawns after the shard is used on the Stash (Telelocator Staff, Using Mobs as bait, etc.) the player can insert all of their easy-to-find antlers to turn into Bone Shards, as another Klaus will not spawn if the Antler has already been used on the sack.
Deer Antlers were introduced in the Winter's Feast update, alongside the Event of the same name.