Collects Avengers (1998) 24-34, Annual 2000, Thunderbolts #42-44. Earth's Mightiest Heroes vs. Marvel's Most Wanted, and more! The crisis of the Eighth Day pits the Avengers against the unstoppable force that is the Juggernaut, while Triathlon's first day as an Avenger takes the team south of the border and back in time thousands of years! And how does the mystery of Madame Masque match the curse of Count Nefaria?

Captain America, Iron Man, Thor, and a large gathering of Avengers battle evil sorceress Morgan Le Fay in a strange medieval reality.

The European country of Slorenia is dead. Every man, woman, and child eliminated with the cold precision of a machine. And out of the flaming remnants of this tiny Baltic state comes a message from its murderer: Mankind's days are numbered because Ultron has returned! He - or it - is one of the Avengers' oldest, most implacable foes, menacing humanity countless times. But never before has Ultron been this dangerous, this deadly. Now, he stands on the brink of committing global genocide, and rebuilding Earth in his own robotic images. Our only hope is a desperate U.N. strike on Slorenia, led by the Avengers themselves. But will it be in time? Will the strength and courage of Earth's Mightiest Heroes be enough in the face of such overwhelming evil? For the sake of the world, it will have to be! Plus: When you're an Avenger, you're one of Earth's Mightiest Heroes - the first line of defense against the dangers no conventional foe could halt, the threats no ordinary man could withstand. Threats including Dominex, Lord Templar, Pagan, and the Thunderbolts! Collects Avengers #12-22, #0 and Annual 1999.

Fan-favorite creators Kurt Busiek and George Pérez usher in a new era for Earth's Mightiest Heroes! Since the team's inception, the Avengers have always defended humanity against the forces of evil. When duty calls, these legendary champions answer, fighting valiantly until justice prevails. But what happens when their oldest foes strike directly at the team? On the eve of a huge Avengers gathering, an attack by the evil enchantress Morgan Le Fay sends these assembled heroes into a strange medieval reality where nothing is as it seems. Held under Le Fay's thrall, the Avengers have lost all memory of their true identities. Breaking free of Morgan's spell, Captain America and Hawkeye must fight to free their teammates before the Marvel Universe is altered forever! Plus: The Avengers take on the Squadron Supreme! Collects Avengers (1998) #1-11.

AVENGER VS. AVENGER! Thanos has been defeated, but the Avengers' biggest challenge may come from within their own ranks! Captain America makes a discovery that may tear the team apart! And: Witness the origin of one of the Avengers' greatest villains! COLLECTING: MARVEL UNIVERSE AVENGERS ASSEMBLE: CIVIL WAR #1-4.

The Avengers must confront their greatest foe yet: Ultron, the sentient robot created by Avenger Hank Pym, who has seized control of the world's media and destroyed the Eastern European country of Slorenia.