A character in the Marvel Universe, particularly the X-Men aspect of it who had the arcane power of turning his skin into organic steel. One of the members of the second incarnation of the X-Men, he was featured heavily in the comic book aspect of the X-Men, however, in the TV show format, little was mentioned, sans one episode where he helped the 'real' X-Men defeat Omega Red. Has not been mentioned in the X-Men Universe since the last comic appearance.

Piotr Rasputin was born in a little farm in Siberia, but when his mutant power manifested, Colossus suffered the regular prejudice. When the Original X-Men were kidnapped, Xavier invited him to join his new team and he accepted. He became a member of the New X-Men, becoming a great hero. Even with the soul of an artist, Piotr managed to help the team many times. He had a little romance with Kitty Pryde when she used to be called Sprite and later Ariel. When the X-Men gave their lives to beat the Adversary, Roma saved them, transporting the team to the Reaver's base in Australia. Colossus remained there, until the team crossed the Siege Perilous. He was reborn as Peter Nicholas, a SoHo painter. He remained with no memory of his hero past until the Shadow King possessed him. Professor X was able to take Peter out of his control, by reverting his mind to his Colossus persona. After the adventure in Muir Island against the Shadow King, Colossus became a member of the X-Men Gold Strike Team, until great traumas began to happen in his life: first, his brother Mikhail returned from the dimension that he was locked, just to transport the Morlocks to another dimension. After, his sister Illyana, former Magik, died from the Legacy Virus. When with battle against Magneto, Colossus left the X-Men, joined the Acolytes, and stayed with them until Avalon was destroyed by Holocaust. When that happen, he returned to Earth and joined his friends Shadowcat and Nightcrawler at Excalibur. His stay with Excalibur generated sparks with Kitty's then boyfriend, Pete Wisdom. After some time, Piotr began to have feelings for Meggan, but she and Brian Braddock were wed nonetheless. After this, Excalibur disbanded and Colossus, with Kurt and Kitty, return to America. After a fight with Cerebro and his agents, Colossus returned to the X-Men and is currently an active member again.