Many people have asked: How do I beat the first epic boss on GemCraft? Well, I struggled with that same one, and I feel like I need to share my way of beating him. I will list all of the things to do.
*Be level 21 (That is the level I did it it, and you can get to level 21 before the epic boss, just re-do some levels.) *First of all, get through the waves. *Second, when you get to the epic boss, be sure to have 6,000-8,000 mana (And be sure its full, too) *Have atleast one (Preferably pure) grade 6 gems. *Have atleast 4 grade 4 gems *And last but not least, have about 3-4 water trenches.
I know this sounds like a lot, but it is possible. Just be sure to max out the first and second talent walls, and put some into the armor skill. The epic monster will be ready to kill, you probably don't have to go all the way up to the guide, because I got it down to 94 health when it made its second lap, so it'll be pretty easy.
Good luck, and tell me if this helped you at all ^^