The note is from Baroness Anastari, and it describes a ritual that is about to happen in the Plaguewood's central slaughterhouse - just south of where Tarenar is at. This could be where they're holding Gidwin!
Tarenar will want to know about this... and quickly, before it's too late!
Progress
What? Did you find something?
Completion
This is it! If this missive is to be believed, then he's literally right over this hill!