So, what exactly do you make on the revelation that Eikons are actually not the same thing as Primals, and what exactly do you think Eikons are FFXIV Gil?

I kinda get the feeling that we will find out that Primals are basically bastardisations of Eikons, sort of like a imitation Eikon that the Ascians discovered how to summon. I'd think it's likely that these Eikons, unlike Primals, have their own personality, rather than their existence being defined by the summoner. That's my thoughts on it, but I could be totally wrong, I'd love to hear more theories and ideas though

It was said in one of the French translations the Warring Triad are from a different dimension.

Whatever they are, i believe that they brought about the 3rd Umbral Era or at the very least appeared during the 3rd umbral Era. 

Additionally, I think they're what Primals were based off and through the study of the Triads the Asciens were able to make a watered version of them ala Primals.

In FF6 they were powerful beings that transformed (and "tempered") people into Espers to fight for them.... which is similar to how Primals temper people to fight for them and transform them like what Leviathan did with Cpt. Morgan and his crew.

We really don't know anything prior to the Allagan Era ... though I think the Sharlayans might know or have an idea

We know that interstellar/dimensional travel is possible, so they can very well be like Midgardsomnr. From my interpretation he came there in a relatively weakened state and Hydaelyn "nourshished" him back to health and formed a Covenant. 

Either the Triad made a pact with Zodiark or they could buy Final Fantasy XIV Gil be Aliens like Jenova who just ended up going to the same planet with the intention of eating it's aether and are subsequently vying for control.