X-Men and the Avengers: Gamma Quest Trilogy

When the Scarlet Witch of the Avengers and Rogue of the X-Men all disappear under mysterious circumstances, each team's search leads them to more questions than answers. When the X-Men appear to attack a high-security government installation, the Avengers must track down the mutants and learn the truth behind the abductions before it's too late. 

The greatest super-team ever assembled tries to find out who abducted two of their teammates. With the help of the Incredible Hulk, they learn that their foe is the deadly Leader. But the search is more difficult than imagined, for the Leader has the power of the Gamma Sentinels behind him—and another surprise ally.

The X-Men - mutant protectors of a world that fears and hates them, and the Avengers - Earth's mightiest heroes, team up with the Incredible Hulk to track down the evil Leader to his base on the moon. Fighting not only his dangerous Gamma Sentinels but also each other, each team must work through their differences in order to save not only their teammates, but the entire world as well.