Quote Originally Posted by Eydaos View Post
First, Ysale seems to not only summon Shiva, but she retains her own mind through the whole process. Ifrit and his ilk seem to have their own consciousness. This seemed like a point to bring up.
This was explained back in 2.4. Ordinarily someone summoning a primal into their own body would be immediately tempered, thus it would effectively be no different than summoning as normal. In Ysayle's case, however, she possesses the Echo which makes her immune to tempering and thus retains control of her body even when it is occupied by the primal.

The question at this point is whether the Archbishop and his knights all possessed the Echo as well. All thirteen of them were capable of summoning using their own bodies as the vessels and they were all able to remain in full control, even entering and exiting the transformation at will. The only way I can see that being at all likely is if the ascians gave them all the Echo as they did with the sahagin priest yet I don't think it's ever explicitly stated.