WARNING: The following contains major spoilers for Kang the Conqueror #3, on sale now from Marvel Comics.
Kang the Conqueror has become one of the most dangerous villains in the Marvel Universe by conquering time itself. Not every version of Kang is the same, however, and the latest Variant to step into the spotlight has proven to be unlike any that have come before him. Not only has Nathaniel Richards dedicated himself to destroying everything his future self would ever build, but he has proven that he is willing to go to any lengths to do so. Unfortunately, he isn't the only one plotting against his variant, and Doctor Doom arrives in Kang the Conqueror #3 (by Jackson Lanzing, Collin Kelly, Carlos Magno, Espen Grundetjern and VC's Joe Caramagna) with plans of his own.
Nathaniel Richards' personal war against his future self was brought on by the unrelenting cruelty the younger variant had suffered at the hands of his senior. After leaving the Kang who had trained him for dead on a primordial Earth, Nathaniel slipped away into the timestream only to end up in the middle of Rama-Tut's reign. This other older version of himself was somehow even worse than the one Nathaniel had just escaped, but still not powerful enough to keep him from continuing his hunt. Years later, Nathaniel was given another shot at taking down Kang the Conqueror following the villain's very first battle with the Avengers (as well as his first appearance) in 1964's Avengers #8 (by Stan Lee and Jack Kirby). While it may have been Nathaniel's best chance to kill Kang once and for all, it was also the moment that Doctor Doom decided to make an entrance of his own.
Nathaniel's tense confrontation with Kang is interrupted when Doctor Doom steps through a portal. Nathaniel isn't particularly upset by this intrusion, especially considering that it was his seeking out Doom's library that originally began his adventure.
When the young time traveler attempts to form a pact with Doom, he discovers that the metal-faced tyrant instead wants to destroy both him and his variant. From Doom's perspective, this is his chance to finally wipe Kang's name from the history books entirely by terminating both versions of the conqueror.
As it turns out, this isn't an easy feat to accomplish, especially when the two enemies put aside their differences and decide to work together against their common foe. Despite having the element of surprise, Doom proves to be no match for the combined force of the duo. By combining their efforts, the two are able to keep their assailant at bay before jettisoning him from the ship completely.
That Doctor Doom would take it upon himself to rid the universe of Kang's influence isn't particularly surprising. Neither is the fact that he lost this particular battle. The biggest surprise is that Nathaniel actually found it within himself to work alongside the person he despised enough to hunt through time, even if it was to save himself.
Whether or not that trend continues is still to be seen, but there is no doubt that both versions of Kang have made a powerful new enemy. Assuming he lives long enough to face Doom again, perhaps the young Nathaniel Richards will be resourceful enough to face the villainous tyrant alone.