Quote Originally Posted by lololink View Post
Ultima Weapon traps the primals and prevents them from being summoned again.

Same goes for the seal from mor dhona and Dalamud trapping Bahamut, all Allagan techs were aimed so that primals couldn't be summoned again.
I agree on the Allagan technology parts. That was the idea behind Dalamud, so that the trapped Bahamut couldn't be summoned again (because he was already manifest and trapped), so I can only presume that, that is proof of a Primal's ability to only be manifested in one location at any given time. As for the continuous mention of a "seal" on Lake Silvertear, I don't actually know where that's coming from. As far as I know the lake is spoken of as the font of aether for Eorzea and the explosion we see is a large amount of aether washing over the realm.