...I don't think I could go there safely on my own.

[He'll have to hope for the best. But given everything that's happened in their own world, he's confident if anyone could revive Estinien, it'll be Himeka.

But as for the entity...]

Aye, I do. They're called primals.

The easiest way to explain them would be "gods created by people". They tend to be incomprehensibly powerful, and have the ability to bend those who don't have a natural shield against their aether being corrupted to their will. It's called "tempering", and until incredibly recently it was a fate worse than death.

Himeka is one of the few that could kill one without that risk, but I've no idea if the Blessing of Light protects her here.

It doesn't explain how I was able to have that corruption expelled from me, however. I have no such protection.