After regaining the Latverian throne from Zorba, Doctor Doom took the orphaned Kristoff under his care and had him raised in the royal palace. He then adopted him and made him his heir. He has since been both an ally and enemy of the Fantastic Four.
When Doom seemingly died at the hands of the Fantastic Four, one of Doom's failsafe plans was set in motion. His Doombots implanted Doom's memories into Kristoff. This caused Kristoff to believe that he was Doctor Doom. When Doom returned, Kristoff believed him an imposter and put Doom vs Doom. Eventually, Kristoff's identity was returned.
After the death of Onslaught and the Heroes Reborn era, Kristoff disappeared. He secretly began searching for ways to take control of Latveria. He created his own limited-use time machine and began his plot, first pitting Namor against his father long enough for Kristoff to sneak into Castle Doom and teach himself the sorcery Doom never taught him. Dabbling in the Black Arts without a mentor caused damage to his sanity.
It is later revealed that he manufactured the Venom Bomb in an attempt to get Doom incarcerated and replace him as despot. After Norman Osborn released him he plotted to recruit the FF to assassinate Doom. Kristoff believed that the members of his surrogate family had abandoned him and attacked them when they declined to help him. Kristoff eventually realized that the Fantastic Four truly cared for him, but still chose to go alone in his mad plan to destroy Doctor Doom and supplant him on Latveria's throne.
Power Suit - His nuclear-powered, micro-computer enhanced armored suit contains an electrically powered exoskeleton which enables him to lift 2 tons; the endoskeleton lets him move easily while wearing this armor. Through the study of a not fully matured Inorganic Technotroid, Kristoff has developed a nearly indestructible suit of armor claimed to be more powerful than Doom's.
Weapons - access to technological weaponry and vehicles.
Magic - Kristoff has the same mystical knowledge of the original Doctor Doom. Unlike Doom he is willing to use Dark Arts and physical combat against his foes. Doom prefers to use his intellect.
Height: 4' 3" (6' 7" in Armor)
Weight: 103 lbs (293 lbs in Armor)
Earth-982 - MC2
In the MC2 Universe, Kristoff is a member of the Fantastic Five, having betrayed Doom and giving up his rightful place as Doom's heir.
Kristoff ruled Latveria as Doom once again, where he would encounter the West Coast Avengers. To their surprise, he let them leave Latveria. He stayed the regent until the original infiltrated the Castle and uttered a codeword that reverted Kristoff to his original personality. He stayed in Latveria for several years, even dating Cassandra Lang for a while. Following an attack by the Avengers, Kristoff revealed that he was trying to keep other powers from obtaining Dr. Doom's technology since his defeat at the hands of the Fantastic Four years ago. He transported the castle to a safe location and later joined up with the Fantastic Five. Dr. Doom, imprisoned for years by the Sub-Mariner, finally breaks free, and imbues countless robotic duplicates with the Power Cosmic. Just one robot manages to decimate the Five and destroy Ben's robotic implants. Although the team manages to stop the robot by trapping it in a stasis beam, the real Doom appears and banishes the younger members to a spaceship orbiting earth, and trapping the others within Mr. Fantastic's own rubbery body. Franklin has the others remove the inner shielding of the ship, and exposes himself to a massive amount of cosmic rays, which increases his powers dramatically. He manages to destroy the Doombot guarding them, but is greatly pained by using his increased powers. Doom, seeking to humble Reed once and for all, has the other freed from his body, and has Reed and himself plugged into an Infinity Device for a mental duel, the loser of which will have his mind sent to the Crossroads of Infinity. Reed's teammates use the opportunity to escape, and with Kristoff's help, shut down the cosmically powered Doombots. Reed and Doom are shown to be evenly matched in their duel, and both minds are sent to the crossroads as a result, leaving their bodies blank and motionless. Sue and Kristoff decide to remain in Latveria and look after Reed, while Alyce goes home with her mother. Ben's son Jacob takes Reed's place in the F5.
In the House of M reality Doctor Doom is leader of the Fanatic Four which consists of himself, Invincible Woman ( Valeria Von Doom), Inhuman Torch (Kristoff) and The It ( Thing).