Now, formatting aside, I think this card would be extremely OP because of the amount of HP buffs (Chaos Power, Blessing, Momentum) and Fractal would be deadly. I recommend that you both decrease the damage ("number of you own, divided by 30" would make it do the same amount of damage as Fire Bolt/Lance) or make it immaterial so that it will die after one attack. If making it un-fractal-able or un-buff-able was not part of your card idea, then I suggest drastically reducing the damage it can do.
I edited this because it making it "number of fire you own, divided by 30" would make each Flash Fire do dramatically less damage than Fire Lance. The damage between Fahrenheit and Fire Lance is at a 2:3 damage ratio. Fire Lance usually does
more than Flash Fire, which makes my "speeds up fire stall" point not as true, as I was arguing with replacing Fire Lance with Flash Fire. In addition, Flash Fire can be stopped by more shields than Fire Lance can and Fire Lance can be used as creature control.
-snip-
Make Flash Fire's attack X, where X = # of fire quanta you have/20.
OR
Give the ability a damage cap. I think a damage cap of 5 would work.
A damage cap of 5 would make it quite UP. OTKs aren't OP, a damage cap of maybe 20 would still be okay.
24
and two Ruby Dragons give 30 damage per turn.
24
and two Fire Lances give 12 damage for one turn.
24
and two Flash Fires give 14 damage for one turn.
72
and six Ruby Dragons give 90 damage per turn.
72
and six Fire Lances give 121 damage for one turn.
72
and six Flash Fires give 96 damage in one turn.
Now, if Fire Lance weren't in the game, this card would be perfectly balanced. However, since upon implementation of the card into the game would allow you to include 12 high-damage cards into a mono-fire deck. Screams OP, but I don't think there's any way to reasonably nerf it. Maybe you should increase the card cost to something extremely expensive so that it can't be used as well in synergy with Fire Lance...