maderas

It's inaccurate. There's a few spells with buggy descriptions.

I don't think Thaos was bragging about the atrocities he'd committed, per se, merely pointing out that the Hollowing of the Dyrwood was pretty small fry in the grander scheme of things. I don't think he was blind to the Pyrrhic victory his solution entailed, either. The vision you have after his defeat was of a huge group of Engwithans sacrificing themselves to their machine in order to create a god (or gods). Seeing as there are no more Engwithans, the implication would seem to be that this wasn't an isolated event. He mentions something about not letting that sacrifice be in vain. As the main character can tell him: he's lied to everyone, himself most of all. He refuses to even consider the idea that the Engwithans may have been wrong, because to do so would mean their sacrifice was meaningless.

So what ultimately happened to the engwithans? Thaos' spirit implies they all sacrificed themselves in order to create the gods, but his memory of a room full of people willingly giving up their own livse and the lives of their children doesn't really jive with Thaos' outlook on humanity - that ruthless individualism would tear civilization apart without the fear of deities.