Klaus is a BossMonster exclusive to Don't Starve Together, introduced in A New Reign. He resembles a larger version of Krampus. He spawns after a player puts a Deer Antler in a Loot Stash, which will return Bone Shards due to it being an incorrect key. He spawns with one red and one blue Gem Deer. Killing these Deer will increase his damage, health, grant him 64% damage resistance, and causes him to grow slightly bigger as well. He is also able to spawn a pair of Krampii during the fight.
After killing him, he will be revived, losing the chains around his body, and allows a large mouth from his stomach to gain a new long-ranged "chomp" attack.
Once he's killed again, he will drop 2 Charcoal, a Monster Meat, 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 Gem Deer are still alive when he's killed, they will turn into normal No-Eyed Deer, dropping their corresponding gem.
Like few other mobs, Klaus has a seasonal color change. During Spring - Autumn, Klaus' horns are dark brown with chains colored in iron. During Winter, his chains are golden with horns being white with red stripes.