Pandemonium may well be Lahabrea's personal research laboratory. We know from dialogue and the short stories that Lahabrea was an "create first, ask questions later" style scientist. The bosses within will probably be drawn from FF 2 and 9. We may find either a clone of Lababrea or some other created being that carries his memories, in part or in whole.

The festival that comes up at the end of Eden may be the "farewell" to the first. They could also run parallel quests with it as the Beast Tribe series final quests.