Commander Keen X Bio Menace is a crossover Keen mod between Keen 4 and Bio Menace 1. The game takes place in the two worlds; on the Shadowlands and in Metro City. Keen's task is to get a chip for Snake Logan in order to open the closed door in Dr. Mangle's lab. The purpose of this game mod is to "warn" people that Bio Menace is the only game that uses the original Keen 4-6 engine. The game contains custom Keen 4 and Bio Menace 1 levels, including some musics, some enemies from the two games.