Ys vs. Sora no Kiseki: Alternative Saga

Ys vs. Sora no Kiseki: Alternative Saga (イースvs.空の軌跡 オルタナティブ・サーガ) is a crossover fighting game developed and published by Nihon Falcom for PlayStation Portable in 2010. It is a spin-off title in which characters sourced from primarily Ys and series are drawn into battles.

Setting
Ys vs. Sora no Kiseki: Alternative Saga follows the setting of Nihon Falcom's celebrated PC-98 game Xanadu, in which otherworldly warriors are summoned to defeat Dragon King Galsis, who has been revived in Xanadu, a world formerly celebrated as a paradise.