Ozzie's Fort is the 4th event in Chrono Trigger. This is where Crono's party puts an end to Ozzie's reign in the Middle Ages.
One of the tasks before facing Lavos is defeating Magus' old henchmen.
Ozzie took over after Magus disappeared so Crono's party heads to Ozzie's Fort in 600 A.D. The party faces Flea Plus, Super Slash and Great Ozzie individually and together. The three former henchmen of Magus are eventually defeated and Ozzie's reign comes to an end.