I, for the life of me, can't figure out if this is broken, or trash. Negative Red Mana is melting my mind right now.

So, you have to have spent during your regular turn? Then this is free? Otherwise you can't cast it? (Those are all, in fact questions? These in the parentheses are not, because I control a Question Elemental?)

Style-wise, what if rather than negative mana, it used a negative image of the mana symbol?

It It would have to have been spent during the fossil turn (like I mention in my comment on Challenge # 031 that previously spent mana would be horrible if combined with fossil turns.

I'm not familiar with a negative image though. A black circle with a red fireball in it?

Why wouldn't you use the fossil supertype and make this a fossil sorcery?

You replace each color with its opposite color, so it would be a green circle with a white fireball. See Wikipedia.

Update: I give up! I can't link to URLs that have parentheses in them. (Edit by Alex: Link fixed :) )

Is the converted mana cost supposed to be 2 or -2?

I like the idea of negative mana symbols. Although maybe 'splice onto spell with RR -- 0. No mana cost.' is as good?

So every mana that you spend during your normal turn is added to your pool as negative mana for your fossil turn? Interesting. Very hard to keep track of, and possible unworkable, but still interesting.

Will an impact ever be paid with mana that wasn't spent this turn yet? Because otherwise creating a fossile supertype and generalizing zhe rule to the supertype rather than the mana symbol seems the way to go; why isn't this a "fossil sorcery"?

Also rather than a negative image, you could invert the color table i. e. a black circle with a red symbol - much more pleasing to the eye. Overall I'd probably go with a special "fossile" treatment (maybe a gray/brown circle around the mana?) that keeps the actual symbol the same.