Piotr Rasputin possesses the ability to turn his skin into steel. While in this form, he possesses incredible strength and durability. After his sister Illyana died of the Legacy Virus, Colossus turned on the X-Men and joined Magneto. He later re-joined the X-Men and sacrificed his life to create a cure for the virus that took his sister's life. Recently he was discovered to be alive, having been captured by an alien named Ord moments before his death. Ord was using Piotr as a test subject for a cure for the mutant gene that gives all mutants their amazing abilities, but the X-Men saved their former teammate.

Colossus also exists in the Ultimate universe. Rather than growing up on a farm, this version of Piotr grew up as an enforcer for arms dealers. Unlike his 616 counterpart, it has also been implied that the Ultimate Colossus is gay.