i like the idea, but l sort of agree with rook that it would probably be better with a limitation, be it weapons, spells, creatures or abilities. or ot's suggestion that it should have a turn limit if not.
also, i understand that fire is your favorite element and this card certainly fits, but it scares me to death considering rain of fire and fire bolt tics and fire shield and your own creatures getting first whack at using this ability.
basically, this card is too broadly reaching and within mono fire would have too much of an impact for my liking, personally