Mana Bomb

how about make it, deal damage equal to 20/40/60/80% of there mana and also take it. Something like that.

What happens is you cast the spell and a bomb is created, then after 4 seconds or so it blows up, dealing damage, and burning mana from units within range.

Please comment if you dled this spell. K Thx
-Monky-Master

What does it do?