This is the final gameplay. Honestly this ending sucks sucks sucks candy ass big time. But it is japanese so ....yeah.
So if you dunno wats happening here, the 16 colossii were only 16 different parts of the same entity, the great Demon Dormin.
Wander actually came here to revive Dormin. Coz dormin promised to fulfill one of his wish. And wander's wish is to revive his beloved. Anyways, this is wat happens after the ritual is complete and dormin revives.
