Suppose you visited an early dungeon but encountered three final bosses

Tatoeba Joban no Danjon ni Dekaketeittara Rasubosu ga Sannin Ita Yō na Tenkai (たとえば序盤のダンジョンに出かけて行ったらラスボスが3人いたような展開)

Micona meets Shōma and a priest named Father Sou. Meanwhile, the king asks Lloyd and his friends to defeat a giant snake in a new dungeon. Sou decides to defeat the snake first. Alka enters the dungeon to find Sou. Marie finds Micona in the dungeon infected by a treant. Lloyd fights Micona but is hurt when he protects Selen and Phyllo. Micona claims friends have made him weak, but Lloyd claims they helped him become a real soldier and he defeats her. The snake is awakened and reveals he is Vritra, Guardian of Kunlun and a source of Alka's power. 

Sou appears and kills Vritra, but Vritra reveals Selen's belt is made from his skin and he avoids death by passing his soul into it. Alka admits she inadvertently created it years prior. Sou teleports away, promising to unlock Kunlun's dungeon. The dungeon then collapses so Alka teleports everyone to safety. Due to a mix up, Allan is credited with defeating Vritra, so the king grants him the title Dragon Slayer. Lloyd realizes Sou is the name of a villain from a Kunlun fairy tale. Alka later kidnaps Selen and Vritra, claiming she needs them in Kunlun.