Concerns regarding Underverse & the questline

[Roger Smith]

I mean, as I've said before, maybe the simple act of you being back topside at all is enough. Diablo is the Lord of Terror. Him sending you back topside could be all he needs to do to get the terror flowing, to let people know there IS a way back out of the Underverse, and to get them to panic and lose that sense of relative security that the Underverse is the most secure place there is, that it's an unescapable Hell.

That seems pretty clearly like you're being an agent of his schemes just by existing.