
Avengers/Ultraforce

The Avengers/Ultraforce event was a two-part intercompany crossover between Malibu Comics and Marvel Comics. The first issue, "Avengers/Ultraforce", was written by Glenn Herdling with art by Angel Medina and M. C. Wyman. The sequel, "Ultraforce/Avengers", was written by Warren Ellis with art by George Pérez, who also illustrated wraparound covers on both issues.
Plot.
The Asgardian god Loki enters the Ultraverse and collects the Infinity Gems from the possession of various Ultraverse's heroes, also discovering the existence of a seventh Gem: Ego. Loki learns the Infinity Gems were originally part of a gestalt entity known as "Nemesis". The Ego Gem possessed the Avenger Sersi when she arrived to Ultraverse from Earth-616.
The slaying of Nemesis caused a reality-changing effect in the Ultraverse called the Black September.