I assume Immunity means it cannot die? I feel like it's pretty strong, you don't really need any setup except pillars, since the condition will happen anyway, so all you need is possibly some healing to keep your hp in control until you can play this. Personally I like my idea better, if I change it to count both player's field. Should probably change the element to something else, since right now it competes against fire bolts in the same element. Maybe Death or Earth?