Crystalis, originally released in Japan as God Slayer: Haruka Tenkū no Sonata (ゴッド・スレイヤー はるか天空のソナタ, lit. "God Slayer: Sonata of the Far Away Sky"), is a 1990 action RPG/action-adventure video game produced by SNK for the Nintendo Entertainment System.Though Crystalis never became a runaway hit, it is now considered a cult classic.