Klaus is a BossMonster 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 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.
The name Klaus is a short form of Nikolaus, referring to Saint Nicholas, the historical origin of Santa Claus.
Even though he was 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.
Klaus is the only boss to have two different boss battle themes.
Klaus in his "idle" state. Note: All these screenshots are of the normal klaus, rather than the current "winter" klaus.
Klaus in his normal "Attack" state, showing the first swing.
Klaus in his normal "Attack" state, showing the second swing.
Klaus in his "command" state, which he uses to cast spells from his Red or Blue No-Eyed Deer.
Klaus in his "laugh" state.
Klaus in his "transform" state, which happens when both of his No-Eyed Deer are killed, making him enraged and have triple the amount of health.
Klaus in his "resurrection" state, which happens after the player kill him for the first time, he will revive and has to be killed again.
Klaus in his "Chomp Attack" state's preparation part, this attack is a long-ranged jump attack.
Klaus in his "Chomp Attack" state's bite part, this attack is a long-ranged jump attack.
Klaus in his "death" state, he will finally drop loot which allows the player to open the Loot Stash.