Go outside of the tavern at 3 am and you will encounter it
You can fight gargoyles in the dungeon [requires a torch] to get moss
Talk to chief nauxus first and if he mentions about Selye being missing, check the areas ive enumerated in order to fight him
Be prepared that he has 2 phases both with 300 hp. Be wary about the notifs that will appear by the top right because he has a heavy attack.
Does anyone know how to get blood crystals yet?