Origins, Chapter 3, Part 2, #10 . Win in 7 rounds.

Valdagorian-2016

Story, Origins, Chapter 3, Part 2, #10 (Meteorite).
Win in 7 rounds.
First, not a totally new player. All my Plainswalkers are max lvl, and my win ratio is a tick over 80%.
Second, I have been spending the yellow crystals chasing after cards, 1200 so far.
Third, this is the last achievement needed to have 100% completion for the story line.
Using Koth of the hammer.
The scenario seems unwinnable, have tried what feels like about 200 times. Has anyone else attempted it? Did you complete the mission? Who did you use? What cards? In how many rounds?
If you haven't tried it, please do.
Any tips would be greatly appreciated.
Thanks