Primal Summoning Question.

[Anonymoose]

To a lesser extent, Egis can still exist despite the Primal being around.

If I'm reading the information we have about Egi properly, we might be able to explain this particular concern.

When you create an Egi, you dilute your aether to do so. In fact, it's possible to divide your aether in a way that you lose your grip on yourself and die; dissolving back into the Lifestream. When a deiform dies, both the re-materialized essence and the aether acting as a catalyst for its form likewise dissolve back into the Lifestream. Now, think of your aether as being sort of like magnetic tape (a cassette). If I am interpreting the knowns properly, what happens is that the fading deiform's aether "taints" your own - effectively "recording" itself onto the "cassette". This attunes your aether to the defeated deiform. When you conjure an Egi, you create an arcane construct out of your own aether while tapping into that attunement; "playing back" the "recording" while visualizing the defeated deiform. For Ifrit, for example, this was made easier by tipping your aether's aspect towards a fire charge, facilitating the "playing back" of the essence of Inferno.

HOWEVER, none of this is a guarantee that the taint on your aether does not in fact itself contain a trace of the origin-essence that answered the beacon.
I can't prove that. So it's probably better to leave the door open a crack.