An easy way that I found to get this achievement.

Just get the spell pack that has the STATIC STORM ability. It attacks all enemies for 10 damage.

Then you just need to get to area 5 where you will wait for a Gemefied Cannon to appear. Do not kill any of them and let their turn happen. They will fire a massive line across the board dealing damage and leaving crystal barriers. You then need to activate STATIC STORM and target those barriers. If there are 8 or more barriers then BAM! ACHIEVEMENT GOT!

Hope this helped someone. Was driving me crazy trying to set up a kill chain.