Klaus

Klaus is a Boss Monster exclusive to Don't Starve Together, introduced in A New Reign. He seems to appear as a bigger version of Krampus. He spawns after a player puts an Deer Antler in a Loot Stash, which will return Bone Shards due to it being an incorrect key. He spawns with two No-Eyed Deer, one with a Red Gem and one with a Blue Gem, engraved into their heads. Killing these Deer will increase his strength. He is also able to spawn 2 Krampuses during the fight

After killing him, he will be revived, losing the chains around his body, and gaining a new long-ranged "chomp" attack.

Once he's killed again, he will drop 2 Charcoal and a Stag Antler which is the proper key to use on the Loot Stash. Opening the Loot Stash will yield around 6 Gifts/Presents. If the No-Eyed Deer are still alive when he's killed, they will turn into normal No-Eyed Deer, dropping their corresponding gem.

Trivia

 * The name Klaus is a short form of Nikolaus. It is also a German given name and surname.