As of v0.77, “portal bosses” have been added to FFVCD. The concept behind Portal Bosses is that a custom boss is created from scratch as an end-game alternative to fighting Neo Exdeath. Upon seed generation, one of the final settings is to choose a Portal Boss, the default of which is SomberMage, the first boss created for this effort. Each boss has a custom AI script, various forms and weaknesses/resistances. Fighting the seed's Portal Boss is completely optional, but does trigger the credits after completing.

• Defeat a boss at one of the three meteors in World 1 among Karnak, Walse or Lonka Ruins, then walk into the warp portal at one of those locations
• Obtain all 4 Tablet Key Items

Finer details about each boss will not be provided - the goal is to experiment and figure out the bosses strengths & weaknesses. If you're very interested in learning more, you can refer to https://github.com/caerulius/FFVCareerDay/blob/master/utilities/data/tables/portal_bosses.csv and https://github.com/caerulius/FFVCareerDay/tree/master/utilities/data/portal_boss_ai from the source.