Get rid of the stealth or slow the boss down. You’re crazy if you think I’m going to blow five hours by playing the second level to get the upgrades to get a brilliant tag.
Use a meteor spell RIGHT when the boss gets out. He’ll pop stealth and then set towers near your gems because his stealth will let him get far enough to get close. Crypts will destroy him, unless you chose a different path. If that doesn’t succeed do other levels and gain stat points.