I just finished the quest where you'll investigate the house of mercer frey and I found this many thanks letter addressed to M which is Mercer but who is R?
Though I was reasonably intrigued by the Many Thanks letter in Riftweald Manor, I was more interested in and amused by A Warning in the Ragged Flagon from Vex to Delvin
Though I was reasonably intrigued by the Many Thanks letter in Riftweald Manor, I was more interested in and amused by A Warning in the Ragged Flagon from Vex to Delvin