Avengers Forever, Vol. 1 #3A (1998)

City at the Heart of Forever
As the time-tossed Avengers battle Immortus? army, they are given refuge in Kang's Chronopolis, a city of time. They escape the overwhelming odds in Kang's time ship at the last second before Chronopolis is destroyed. The city's energies then coalesce into the Forever Crystal, a powerful time artifact.
Release Date: 1998