Let's check out the note on mekel's corpse. fortunately it's still legible, even with the bloodstains saturating it.
So we head to the elven alienage and inspect their most sacred of trees, which they apparently also allow people to cut chunks out of to make hammers for the biannual dog lord and apostate stomping.
Valerie finds a note on one of mercenaries' eviscerated corpses. Again, it's somehow still legible despite presumably being soaked in blood.
So we head to the cave where they first met. How Valerie knows which specific cave the note is referring to is never explained, but it probably has something to do with there only being 2 cave maps in the entire game.
And finally we meet the mysterious mastermind pulling the strings.