Use Baron Blade at Insula Primaris. Have Legacy in the first slot, Fanatic, Haka, Ra, and then Tempest in the last slot. This will allow you to do at least 12 damage per round and 17 damage per round once Obsidian Field comes into play. You will need lots of damage to take out the Baron's minions and platforms. Select Tempest's attack order carefully to get a few more points of damage. When Volcano appears, have your teammates all turn on Tempest and knock him out. Next, use Tempest's knockout power to give your teammates immunity to fire damage. Having Volcano damage all enemies and no damage to you makes this easy.