Claus is the deuteragonist and secondary antagonist-turned-anti-hero of Mother 3. He is the teteragonist of the Mother/EarthBound series. He is the "commander" to the Pigmask Army, the biological son of Hinawa and Flint, and the older twin brother of Lucas. He is the "Negative" one of the twins, as he is left-handed and carries the sword of Despair, Tyrfing. He was a sweet boy like his brother, but after he was brainwashed by Porky Minch, he was forced to kill everyone who was resentful towards Porky, including his own family. Despite this, though, he is not consciously evil; nor is Lucas' evil counterpart; they both just fight for their own justices.
He and Lucas are one same genetic being sliced in half, as are all twins.
Claus, as Lucas' twin brother, looks nearly identical to him. He formerly wore clothes that are similar to his brother's; with the colors opposite, cyan and yellow. He has red hair in a similar style to Lucas'. He wore orange pants, white socks, and cyan-white shoes.
Claus currently wears a long-sleeved, yellow shirt with a gray coat, orange trousers, and gray boots. He also wears a mask to cover his face, especially covering his left eye. He also wears an arm gun in his right hand, and wields Tyrfing in his left hand due to him being left-handed. His eyes, normally teal with long eyelashes, turn red in his later individual life.
Claus was living happily with his family. Years later, they had to leave Alec to see Flint. However, on their way, the trio were attacked by a Mecha Drago. Hinawa risks her life and dies for her sons. This made Claus become angry and go missing from Tazmily Village. While everyone was grieving Hinawa's grave, Lucas reveals that Claus has gone to avenge his mother by killing the Mecha Drago, stealing his father's knife.
However, on his way, he fell from of a cliff, and the Pigmasks found him, brainwashing him and turning him into the Masked Man.
Claus needed to pull the seven needles to help Porky, but Lucas and his crew stop him, fighting him. Claus flies away.
Before the final battle against Claus, Flint reveals to Lucas that the "Masked Man" was actually Claus. This forced Lucas to guard until his brother comes to his senses. Thanks to Hinawa, Claus was able to come to his senses, but eventually suicides so that his brother can pull the final needle. He apologizes to Lucas and his father and says that he will be going to "that place" where his mother is, but is sure they will meet again someday, before giving his final breath.
- Claus' name is an anagram of Lucas' name.
- Claus is the only main character of the Mother/EarthBound series who is an anti-villain.
- Claus was originally going to be the protagonist of Earthbound 64, but this was changed when it became Mother 3