Warning: The following article contains spoilers for Doctor Doom #7, by Christopher Cantwell, Salvador Larroca, Guru-eFX, and VC's Cory Petit, on sale now.
Outside of being the Marvel Universe's ultimate villain, Doctor Doom is also the monarch of Latveria. This fictional, Eastern European nation has bowed to Doom's rule for most of the villain's history. Most recently, Doom's forgotten prince returned to his rightful place in the nation's castle: Kristoff Vernard, Doom's adopted son.
Kristoff first appeared in Fantastic Four #247 by John Byrne. This issue saw Doom, along with a reluctant Fantastic Four, attempting to reclaim Latveria from the tyrannical rule of Zorba Fortunov. Despite Latveria's new leadership, Kristoff and his mother were avid Doom-supporters, illustrating an understated benevolence to the Latverian ruler. Unfortunately, Kristoff's mother was killed by one of Fortunov's robots. This murder left Kristoff orphaned, at least until Doom regained his throne. Feeling sympathy for the young boy, the Latverian king adopted Kristoff, raising him like a son. More importantly, Doom made Kristoff his heir, grooming the boy to inherit the Latverian throne.
Later on, Doom was seemingly killed, once again orphaning Kristoff. Yet Doom's robots ensured that his legacy would live on, programming Kristoff's mind with all of Doom's memories. As a result, Kristoff's personality was supplanted by his father's, making the child believe himself to be the real Victor von Doom. Acting as a pseudo-Doom, Kristoff undertook various schemes against Reed Richards and the Fantastic Four, even improving upon some of Doom's oldest plots. For example, the first thing Kristoff did was take the FF's headquarters, the Baxter Building, and send it flying into space.
This time, however, Kristoff did not make the mistake of allying himself with the Sub-Mariner, as his father did before. Even so, Kristoff was eventually foiled by Marvel's First Family, who captured the boy and took him back to New York. The Fantastic Four hoped they could ultimately restore Kristoff's personality. However, the real Doom returned, inciting Kristoff to confront his adoptive father. Believing Doom to be an imposter, Kristoff battled his father for the Latverian throne. This began a long series of civil wars in Latveria, where one Doom was deposed and the other reclaimed the throne. After a while, Doom managed to restore Kristoff's true personality, ending their conflict.
Later on, Kristoff was recruited to aid the Fantastic Four on their adventures. The heir to Doom's throne joined the super-team, alongside Scott Lang, the second Ant-Man. Kristoff even developed a crush on Lang's daughter, Cassie. Ultimately, however, Kristoff returned to Latveria, standing beside Doom as an adviser and heir to the throne.
Absent in the comics for quite some time, Kristoff recently returned in Doctor Doom #7, by Christopher Cantwell and Salvador Larroca. In this issue, Kristoff is seen alongside the rest of Doom's Latverian inner circle when the monarch returned to his castle. Following his return, Doom tests the loyalty of each of these Latverian figures, one at a time.
When Kristoff is brought before his father, the young man shows immense loyalty. Kristoff refers to Doom as "father" and expresses joy at his master's return. Yet Doom does not reciprocate these warm feelings. Rather, the Latverian monarch looks down upon Kristoff, dismissing him in a very curt fashion and telling the young man to "never call me father again." Although Doom seems to have disowned Kristoff, for the longest time, there was an heir to the Latverian throne. Upon his return to comics, Kristoff may yet make another claim for his rightful inheritance.