Colossus, also known as Piotr Nikolaievitch Rasputin, is a superhero in the Marvel Comics universe. He was created by writer Len Wein and artist Dave Cockrum and first appeared in Giant-Size X-Men #1 in 1975.

Colossus possesses the mutant ability to transform his entire body into organic steel, granting him superhuman strength, durability, and the ability to resist extreme temperatures. He is a skilled hand-to-hand combatant and is proficient in the use of various weapons.

Colossus is a member of the X-Men, a team of mutant superheroes who fight for peace and equality between humans and mutants. He has been a prominent member of the X-Men for many years, and has also been a member of other superhero teams such as X-Force and the Acolytes.

Colossus is known for his kind heart and selfless nature, and has often sacrificed himself to protect others. He has a close relationship with his sister, Illyana Rasputin, also known as Magik, and has been involved in many storylines and battles alongside her.

In addition to his role in comics, Colossus has also appeared in various other media, including animated television shows and films. He has become a beloved and recognizable figure in the Marvel universe, known for his impressive strength and selfless heroism.

Overall, Colossus is a complex and intriguing character in the Marvel universe, known for his unique mutant abilities, heroic nature, and close relationships with other characters. He remains a popular and beloved member of the X-Men, and continues to be a significant part of the Marvel Comics universe.