Klaus is a Boss Monster 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 63.6% damage resistance, and causes him to grow slightly bigger as well. He is also able to spawn 2-6 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 4 Bundled Supplies. 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.
- Klaus was introduced in the Winter's Feast update, alongside the Event of the same name.
- The name Klaus is a short form of Nikolaus, referring to Saint Nicholas, the historical origin of Santa Claus.
- Even though he is blind due to his eyes sewn together into a single large "X" shape, it is possible that Klaus has a keen sense of smell to track down the player. This is supported by Klaus occasionally attempting to "Sniff out" the player.
- Klaus is the first boss to have two different boss battle themes. The second being the Ancient Fuelweaver, although the second theme plays when Woven Shadows are being summoned.
- When preparing for the "chomp attack", Klaus looks a bit similar to the Screecher, a creature from the horror mod of the same name made by Klei Entertainment.
- When put to sleep, Klaus covers his eyes for some reason.