Mario and his party discover the mysterious sealed door during their travels to Monstro Town. The seal to Culex's dimensional vortex is eventually broken by Mario, the champion of the Mushroom Kingdom.
Before he leaves for his home dimension though, Culex wishes to battle the world's "strongest knight."
As such, Culex is forced to return to Vanda without completing the Dark Mage's assignment. However, Culex discovers that Mario's dimension was actually uninhabitable by himself and others of his kind. The Dark Knight is sent to Mario's world to fight on behalf of the Dark Mage. According to one of his neighbors, a Piranha Plant, Culex is "always mumbling about Crystal-this and an Evil-that." Despite waiting in a dimensional rift, Culex's next-door neighbors can still hear the Dark Knight talking to himself through the walls. Culex eventually comes to reside in a cross-dimensional region that is found behind a sealed door in Monstro Town, a village of reformed monsters, which is located in Land's End. Before or during the events of Super Mario RPG: Legend of the Seven Stars, Culex crosses over from the dimension of Vanda to Mario's dimension.