Help with Burgeoning Blast

The description reads "A spell that deals 0 damage. Increase this spell's damage by 2 at the end of each turn. (Castable once per battle.)"

When I cast it, it obviously doesn't do damage, but it in increases it after that turn. But I cant cast it again because of the "once per battle" rule. And after each battle it resets to 0 damage.

Is this spell bugged or just useless. Or am I doing something wrong?