Tabletop
Troben will move his echo as a free action and use it to attack Mourne (without disadvantage thanks to Eithne).
- Attack #1 - Soft critical on Mourne for 29 slashing and 9 fire damage (wow!)
- Attack #2 - Hits Mourne for 17 slashing and 3 fire damage.
That's 58 damage to him! If that doesn't kill him, he will use his Unleash Incarnation to get a bonus action attack against Mourne. If it DOES kill Mourne, then this bonus action attack is against the Dredge (although it's due to GWM).
- Bonus attack - Hit AC 19 (which will hit everything) for 12 slashing and 6 fire damage.