Does this mean your
quanta must match the creatures HP exactly? Or will it be able to kill anything with less HP than you have
in your pool?
I'm guessing you mean the latter, since the former would probably be situational and UP.
Its definitely a bit more powerful than a standard bolt for taking down large creatures, so I think it will fit a slightly niche than bolts.
Considering the level of stored quanta needed scales with the targets HP, I think this should be enough to justify a one-shot kill kind of effect...
Of course, you are likely to get people complaining about adding to fire's already abundant CC supply...