As a note, after you beat Mergo, you’ll want to do whatever else you need to in Bloodborne, as you’re very near to the end of the game. If you haven’t done the DLC bosses that we mentioned ...
No matter how many years pass, I will always dread the moment in Bloodborne's DLC where you have to face the Orphan of Kos, one of the most difficult bosses in the entire history of video games.