Questions/Theories About Coil (Long Read SPOILERS)

[Anonymoose]

Bismark was it?

Agrius

as well as TWELVE (ish) other beings.

It's hard to tell if they meant anything by this. In part of the scene where Ifrit is unfolding, you can freeze frame at different times to see anywhere from 7 to 13 silhouettes, but when they all start flying away, I can make out at least 20 glowing projectiles.

What was the light that killed Midgarsomr?

The use of Magitek was resurrected by a people who couldn't use the magi part of that combo, so they replaced the fuel source with ceruleum, a highly unstable substance. Midgardsormr wrought Agrius to ground, and the buckling of the ship caused the ignition of the ceruleum in the fuel tanks. This set off the enormous explosion, killing Midgardsormr and causing enough damage to destroy the seal under Silvertear Falls.

It is the full nature of the seal that is unknown. Silvertear Falls is the center of the world's aetherial network, so we're told, so what was the point of the seal? To keep the aether there? To keep specific aether there? To surround Xandes' tomb with it? To seal the aether containing the primals' essence within it? Did the breaking of the seal simply imbalance the aether of the realm enough to begin a descent into the Umbal era and this is what allowed the primals to be summoned? Or were the primals in the seal in the first place? We know that the Allag could seal primals - even Ultima could trap them. But I find it interesting that Odin was sealed inside a crystal beneath a spring and all the other primals came out of a shattering seal inside a lake... coincidence?

A lot remains to be seen.

As far as the Primal vs. Elder Primal discussion goes, until we get more clues, I'm just leaving it at "they're from a different era." It's the only thing that we can confirm that Bahamut, Odin, and Belias have in common.