He is unbeatable! Now, I know others on this board have played Gemcraft, in fact, it was some right bastard here that turned me on to the addictive thing.
Has anyone beat it?
Several times 
Stupid addicting shiny game…
I just made sure I had the highest level possible, then went for extra towers + water traps + enough life to let him pass once if needed.
Go back to any levels you didn’t get a complete circle on and do those until you do. If you haven’t, make sure you re-spec and move the points out of the lower level talents to the end game ones
It’s been a few weeks since I’ve rehabbed out of my GemCraft addiction, but…
The trick is making sure you have a lot of very powerful purple gems. You’ll want to reposition one or two of them a couple of times to make sure he’s contantly getting bombarded with their Armor Weakening ability. Once his armor is taken out, then the strategies mentioned above all work so much easier. As long as you have the mana to absorb one or two base hits, you’ll be golden.
Side note: Aieeeee!!! I just went to lod the game back up – I couldn’t remember if I was level 82 or 85 when I stopped – only to be reminded of what happens when you get a new laptop. My game…gone! All gone!
Welp, looks like it’s time to start over.
aHA! I was mistaking ‘Hit points’ for the wrong thing. I thought I needed 100k+ points to let it pass through, when all I really needed was a little over 5k. I was blowing my wad of manna every time, when instead I should have built up 20k to allow 3 passes. Once I figured that out, it was easy.
Now nobody mention any other addicting games dammit!
So, uh, Defender over at Kongregate would be right out then.