[Spoilers] Death and reincarnation

[Absimiliard]

And yet Shiva and Alexander managed not to temper anyone around them, so clearly some amount of control is available.

Alexander was contained almost immediately upon being summoned, and Ysayle never actually interacted with anyone she could temper while in her primal form. Truth told we don't even know how her tempering would've worked since she was an actual person transformed into the likeness of a primal through a similar process to summoning.

Tempered them to do what? Everything the Ascians have done involved tremendous death and suffering and chaos, just to prepare the shards and the Source to do their sacrifice to Zodiark. As in, there is no indication that all the deaths and literal world-ending Calamities were part of Zodiark's stated price to bring back the Ancients, but just collateral damage in their efforts to Rejoin the shards to create a proper stage for the real sacrifice.

Tempering does not necessarily come with a set of commands. Most tempered creatures are just blindly, fanatically loyal to the point that they come off as being completely insane. We can again look to Ramuh and for examples of tempered individuals doing things that actually go against of the one responsible for the tempering.

At no point has it been said that Zodiark stated any sort of price for its aid. There is certainly no indication at this time that it wanted sacrifices, only that the Ancients sacrificed themselves to it twice of their own will; once to save the world, once to heal it. The first set of sacrifices were required just to create him, while the second were either needed to summon him again or to replenish enough of his power for him to be able to carry out his task. We know nothing of the circumstances surrounding the third other than that the Ascians believe doing this will bring back their people.


It should also be noted that the rejoining itself will - at least according to the Ascians - have the effect of making their sundered people not inside Zodiark whole again.

Judging by the actions of the Ascians, they clearly have to be stopped. And since they themselves credit their motivations to Zodiark, I don't know what else Zodiark might have expected them to do.

The actions of the Ascians cannot necessarily be blamed on Zodiark itself. For all we know, they might have come up with all of this own their own. Heck, Emet-Selch doesn't even seem to care all that much about Zodiark most of the time other than as a means to bring his people back to life. At this point we just don't have enough information to definitively blame Zodiark for everything.