CCDD 042215—Explosive Reagent

Cool Card Design of the Day
4/22/2015 - I found an old design that was a Shock that triggered a Flame Jab whenever another spell is cast while it's on the stack. That's a bit broader than anti-countermagic since you can combo with it yourself, but referencing the stack is to be avoided wherever possible, and this ability didn't come close to warranting it. Which made me curious if I could find a similar effect without using the word 'stack.'

Explosive Reagent is still a bit too weird for common—even having simplified the rider so it's not a trigger and doesn't target independently—but I quite like the solution of using terminology players are familiar with. Everyone uses "in response" and even in pockets of culture that don't, it's intuitive.

I was thinking the comprehensive rules would need an entry to codify that phrase, but it already exists:

116.7. If a player with priority casts a spell or activates an activated ability while another spell or ability is already on the stack, the new spell or ability has been cast or activated “in response to” the earlier spell or ability. The new spell or ability will resolve first. See rule 608, “Resolving Spells and Abilities.”

It's used in multiple examples, and even has a glossary entry.

That execution doesn't offer any immunity to countermagic, though if I  Force Spike your Negate, it'll deal triple damage. But that's only relevant if I target a player, since I'm either meeting a creature's toughness or I'm not.

To the right is an iteration where all of that does matter, but it carries the added complexity of having a trigger on a spell, which is decidedly unusual. If we agree it's more complex than worthwhile, the original might look pretty good on the face, but in practice it's basically a backwards Grapeshot. Even having found better language for this effect, I don't think I've found a card worth printing. What do you think?