Quote Originally Posted by kyuven View Post
snip
Bahamut simply just overpowered the seal before it could be completed. He was held in captivity for a very, very long time (among other factors, which are Final Coil spoilers so I'm leaving them out here), so when Dalamud burst open we had a very, very pissed off elder primal on our hands - far more than the Twelve could contain. I don't think any of the (soon-to-be) Scions were present for the actual Battle of Carteneau, as they were scattered around Eorzea in prayer at the marks of the Twelve that Louisoix placed so he could channel the populace's prayers to summon them in the first place.

Also, it was stated at the introduction to the original HM primal trio that Thancred was especially vulnerable to tempering thanks to him being possessed by Lahabrea, so at the very least he's basically confirmed not to have the Echo.