Quote Originally Posted by Seraphor View Post
1. You can't summon the same primal twice.
If Ifrit has been summoned, and you try to summon Ifrit again, then the first Ifrit will simply receive all of the additional 'prayer/faith/belief' and grow in power instead.
Maybe. Primal summoning is pretty vague (as is magic in general.) Magic in the XIV universe seems to pretty much all powerful and theoretically anything is possible if you want it badly enough and have enough aether. Everything else is just philosophy and technique. Rules like "can only summon one instance of a primal at a time" seem to be more of a belief than actual unbreakable rules. Someone who didn't know about that 'rule' would probably be exempt from it and could summon as many Ifrits as they wanted.

Quote Originally Posted by Seraphor View Post
2. For 'self primals', e.g. Shiva, Thordan, Tsukuyomi, and I guess Shinryu via Zenos, plus Ryne' Shiva too come to think of it... the Echo is instrumental in controling it.
Probably. Anyone without the temping immunity of the Echo (or resonance in the case of Zenos) would likely fuse with the primal completely and die when it's defeated (Thordan, Yotsuyu.) Ryne has the Echo so she came out of the summoning mostly unharmed.