Tabletop
Go ahead an apply that third hit to the Dredge. Because he took out Mourne, his Greater Weapon Mastery kicks in and gives him an extra attack as a bonus action. So add another 12 slashing (halved to 6) and another 6 fire damage.
Troben will attack the Dredge with advantage!
- Attack #1 - soft critical hit for 25 slashing (halved to 13) and 7 fire damage.
- Attack #2 - soft critical hit for 27 slashing (halved to 14) and 8 fire damage.
He summons his echo again...mainly because he doesn't have anything to do with his bonus action.
Oh, and I forgot to have him make that strength save: Saved!