Seems a bit OP. Also, fix the card so that the ability cost is on it (
). Kael Hate will appreciate it if the table and the card are identical.
As for the card, you could do infinite damage to all creatures on the board? That is ridiculous. If you had a bunch of immortals or just a fiery you would completely dominate with no worry of losing your creatures. Not to mention phoenix.
I suggest a larger divisor, say 10 at least. That or a fixed value but it shouldn't be too high because fire is the element this kind of spell would effect least.
PS I like the pic