The Burn

[Cilia]

The Garleans have been stumbling across Allagan knowledge for a long time - long enough to know to bring the "lunar transmitter" to House Darnus long before the Bozja Citadel incident, and in that incident they decried the loss of a great amount of knowledge left by Allag (consolidated there to help Midas with his restorations). If the Garleans learned the word eikon from Allag, they must have learned what eikon meant, yes?

Perhaps the Garleans knew only abstractly of these entities and the effects they have on the land until Solus saw the Burn.

Flows logically. I also forgot that the summoning rituals were taught to the beast tribes by the Ascians only after Silvertear, though as it's possible to summon without their ritual it could simply be assurance that primals summoned from then on would have behavioral patterns that align more closely with their goals. Easier summoning conditions would provide a golden opportunity they'd never pass up as well (assuming it wasn't of their own making).

That... still leaves Mysterious Primal X, summoned during the conquest of Ala Mhigo, unaccounted for though... I think. Ala Mhigo was conquered before Silvertear, that much is certain, and a primal was reportedly summoned in the region as a consequence.