So we have the Amaurotine society using Creation magic, which is described as the ability to form physical objects out of aether based on a template you hold in your mind. We know crystals can be used to supply the aether for this, since in a sidequest we receive a few crystals from an Amaurotine image to help us Create an Ascian robe for ourselves.
Now we have the surviving Amaurotines, the Ascians, teaching the Eorzean beast tribes and others to use aether to summon Primals using crystals, based again on templates that they are familiar with - the Gods that they worship, in this case.
Seems to me a fairly safe assumption that the summoning arts that the Ascians are teaching are actually just latent Creation magic, right? This also explains Emet-Selch's designation of Zodiark and Hydaelyn as Primals, since they were presumably Created in the same way.
What are the implications here? If the Beast Tribes (and Thordan, and Iceheart, and Yotsuyu, and Louisoix, and Ilberd, and ...) can all do this thing, does that mean that everyone on the Source has the latent potential to perform Amaurotine Creation magic? Does that ability increase as additional Shards are rejoined, bringing the Source's inhabitants closer to their perfected Amaurotine selves?