This is where only Key Tactic will win you the day AND Key Team.
There's a multitude of problems here, so start with what kind of deck you need to bring:
15 card deck to make it reliable. This doesn't seem much, but will bring you through this battle - IF you have the right one. What you'll need is these:
- 6 to 9 Feles with Distraction ability. Make them high HP but low Attack. The low attack is needed for the AI casts Judgement regularly on you, and you need your troops to hold out as long as possible. So here you'll need actually LOW RANK cards! Place them to the upper row (Lane 1) exclusively to block the lane completely thus keeping them alive. Start puting them the back coloumn of the spawning pods if possible, because that means they'll reach the farthest point later, at what point everything dies instantly - nad killing the uppmost guy with its 300 HP is just hopeless. Until Round 6 only put down 6 of these!
- 6+ centaur with hit&run ability. Reason is: they are fast, they won't end up right before the enemy bosses (there are 4 of them), and they have high damage. And not too high cooldown. They will be the ones killing the enemy. Prime job for them is to kill the enemy in the 3rd lane from the top, as that is which cast a spell what kills all of your units, no matter what, at the 5th turn. If you manage to dispose this before the 5th round ends, feel lucky. If anything ends up in Lane 3 before killing this guy, you have to surrender and retry.
- 6 skill cards for warriors, 2-3 skill cards for other classes, which can be: encourage + heroic for warrior; sanctuary / petrify / disinformation for the others. You have to be able to hold up occasional enemy units. The warrior shall cast skills on the first avaiable units landing to speed up the killing process.
- 1 Chief Hrafn (optional): goes into the bottommost lane, starting the closest spot to your heroes. Job is to speed up the killing-process.
Kill the guy in Lane 3 imediatelly, then the one in Lane 2. As Lane 1 will be full of distraction-units constantly, likely the bottom guy dies third - he has the weakest units to spawn if it happens.
Have the person with the highest HP (preferably the warrior, but most importantly the one with the highest HP) in Lane 1 (upper left box in the room). This is because the enemy is able to deal direct damage to your heroes, and will do so to the upmost hero of yours, so oyu have to be able to hold as long as possible. To switch places with a full room the current person taking the place must leave, and the highest HP person must change to his/her place, then the person left shall come back. To be able to go back note the Room Number, and Search for it from the lobby of the Challenge Hall. the remaining crew should kick out random people taking the leaving person's place for being polite.