What level for Reha Arena of Death?

[DGDobrev]

There is another cheesy way. Since the enemy stacks are huge, all you need is one high-initiative unit, 1 tank with 30% phys resistance, gorguanas, target spell and ball of lightning maxed.

Turn 1. If you're playing Paladin or Warrior, use Target on the Tank straight away. Gorguanas cast Mark of Blood on the biggest stack and the pet summons a ball of lightning. With any luck, over 80% of the troop will be gone just like that. If you're a mage, target + stone skin on the first turn.
Turn 2. Cast Stone Skin on the tank. 1 or 2 charges left on the target spell. If you're a mage, flaming arrow on the biggest stack (so that the post effect can diminish their size) and lvl 1 phantom on the gorguanas.
Turn 3. If you have 2 charges left on the target spell, cast lvl 1 phantom on the gorguanas. If you have 1, you're hard pressed to recast it and slap another ball of lightning. As a mage, use mark of blood on another big stack and use ball of lightning again. Spells - target if needed and another flaming arrow to get another troop burning.

At this point, all you need to do is rinse and repeat Ball of Lightning + Mark of Blood from the Gorguanas make the big stacks die faster than lvl 1 units.

[ivra]

I used a similar tactic. Since I did not have Gorguanas in my stack I used Ball of Lightning + Awaken Dragon + Ball of Lightning the first turn. Next turn I used Awaken Dragon + Ball of Lightning. This was very effective on Impossible stacks. If I fought dragons I used Ball of Lightning + Awaken Dragon + Fiery Phantoms. I played as a warrior and it is no problem to have more than 100 in Rage. I made sure my rage was maxed before taking on dragons.

[Zechnophobe]

Arena of death were two almost identical combats for my Paladin. First turn target my bone dragons. They wait until end of turn when all bad guys are around them, and then use their poison AoE attack. Bam, massive damage to 6 stacks. Turn two I time back the dragons at the beginning of the turn (Back to same spot they started in... in the middle of most enemy stacks) and poison blast again.

Whooped on them something fierce. Do it a little different against brontor/tirex army though. Tactics is a huge help in setting something like this up.