I'm not fan at all of adding more hard pc, especially in air.
- means air which already have cheap dragonflies to immolate, access to massive spell damage ignoring most shields with unstable gas and access to massive normal damage with skyblitz to beat mitigation shields would have one more way to beat shield based decks, when it's also one of the strongest elements for creature control (yes fire is in this case, but why make air another fire)
- the spell costing 3 means an immo rush can have that super shield deflag in an usually unused element without touching the fire quantum it uses for phoenixes or golems, making rushes even better than they currently are ; also think about the power of the air/life/light fireflies rush if you add an air deflag
- means a rainbow can have the insane number of 24 hard pc spells in a deck (not even counting butterfly and pulverizer), making any shield but bone wall and protected ones useless ; enjoy the biggest timebow decks having access to pc as often as a 30 cards specialized one
Now I like the idea of the card, a spell targeting shields only (would be a must have for arena decks, as AI is obsessed by hourglasses with actual PC spells) and doing damage ; but I'd rather make it soft pc (ie : your creatures ignore the shield for one or two turns), which would have a great synergy with sky blitz ; or a specialized pc against the annoying total shields (ie : permanently reduce by 2 turns or 5 charges the duration or power of shields having one - a counter to phase shields, bone walls, hope and wings)