Two of the bosses--the Demon Tablet and Marble Dragon--are Amdapori constructs. There's note that the Marble Dragon is too accurate to have been done without reference, suggesting that the creator must have been to Dravania to study them first-hand.
The 'Dead Stars'--Nereid Triton and Phobos--are tasked with managing the weather of the Crescent. Unclear what happens now that they're dead.
And the Magitaur is a voidsent, showing that this isn't entirely the Amdapor Show. Most interesting to me is that it mentions him wielding four weapons from the War of the Magi: the rune axe, sage's staff, assassin's dagger, and holy lance. Now, this is interesting because they're four of the twelve Sealed Weapons from FFV.
Finally, the 'treasure' at the top of the Forked Tower is an archive of texts in a language nobody can understand. Naturally, we don't have any idea what that entails, save that it's probably about the Fifth Astral Era.
I think most interesting of all, though, is the absence: this is only one half of FFV's Forked Tower dungeon, this is the physical tower. The other half is the magic tower that we're getting later, whose final boss is Omniscient. If you've played FFV you should already see where this is going, but if not:
That's what Archive's robe is based on.