Dungeon Hunter 5

This is a story related achievement for mission 12. The stage itself isn't too hard but the boss will be the hardest you've fought yet. His attacks do massive damage, and as a result you'll need to be a bit more careful than you have been. I found running circles around it until it attacked and then attacking it while it recovers was the best way to deal with this boss. Doing that, I was only hit a couple times.

The last thing to note is that sometimes a white circle will appear around it. If you don't get away, it will swallow you and spit you into a lava pit. Make sure to avoid this.