Hulk; Namor, the Sub-Mariner; X-Man; Dr. Doom; Mr. Fantastic; Invisible Woman; Human Torch; The Thing; Franklin Richards; Captain America [Steve Rogers]; Iron Man [Tony Stark]; Thor; Vision; Scarlet Witch; Wasp; Giant Man; Hawkeye; Black Panther; Crystal; Onslaught
X-Men [Professor X; Cyclops; Jean Grey; Storm; Wolverine; Bishop; Gambit; Cannonball; Iceman; Rogue; Joseph]; The Watcher; Hulk; Namor, the Sub-Mariner; X-Man; Cable; Dr. Doom; Fantastic Four [Mr. Fantastic; Invisible Woman; Human Torch; The Thing; Franklin Richards]; Avengers [Captain America [Steve Rogers]; Iron Man [Tony Stark]; Thor; Vision; Scarlet Witch; Wasp; Giant Man [Hank Pym]; Hawkeye; Black Panther; Crystal; Quicksilver; Falcon; Black Widow]; Onslaught (villain); Apocalypse (villain); Foggy Nelson (cameo); Karen Page (cameo); Jarvis (cameo); J. Jonah Jameson (cameo); Robbie Robertson (cameo); Trish Tilby (cameo); Willie Lumpkin (cameo)
Synopsis
The Marvel heroes join the X-Men in an all out attack on Onslaught. Many of the non-mutant heroes are forced to sacrifice themselves to beat their foe. The battle is won, but at the ultimate cost.