What is Zodiark?

[Nalien]

Worse yet, consider Zodiark. He, certainly, does not have enough followers to warrant his existence as a Primal on the same level as Hydaelyn.

That's exactly why I suggest that they are in fact Eikons. Case and point; How many followers does Odin have? None, perhaps one at best if he is tempering someone to manifest himself... Eikons aren't simply a higher level Primal, there seems to be something special about them... Even the Ascians seem to have some distinction between them; They need the Primals for their plan, but, at least based on Unukalhai (who just has to have some connection to the Ascians), they don't want Eikons being released. Why? If Eikons are just stronger Primals, wouldn't Eikons be better to speed up their plans? The only conclusion I can come to is that Primals are bad, and Eikons are good, either that or Unukalhai is innocent, despite that post credits scene at 2.55...

Considering the rather extreme methods of ceremonies that have been required to create and sustain more powerful versions of Primals (ie: live sacrifice for some extreme versions, or tens of thousands of tortured followers in other cases) what would be the nature of Hydaelyn's continued existence?

Funny you should mention live sacrifices... What is one of the key points about life on Hydaelyn? The Lifestream... When NPCs die, they return to the Lifestream, which is a part of Hydaelyn, until their aether (but seemingly not them) is recycled for new life... We even have someone (Y'shtola) who has basically inhabited the Lifestream now, and it didn't seem like a particularly pleasant place to be... Certainly not for clothing, at least...