I choose to believe that your set will have enough enchantments with flying that my deliberate misreading is fine.

Green does get flyer hate - but this is very very strong. At common? Come on!

For what it's worth, I presume Phopus designed this card using Crushing Vines for his model.

Crushing Vines is a common instant. This is a common sorcery that costs an additional colored mana. I can see how Phopus got here. I might also be persuaded that the card is overstrong, but I think I'd rather test it before making that assumption.

Is there discussion about that mechanic somewhere? It would need some hardcore support to make any sense. The flavor is quite questionable as well. Nothing about it really 'jells' well in my book.

Highstorm is about as flavorful as retrace and would get some mad mechanical relevance if that mechanic was in this set as well.

Retrace works 'fine' as delivered tough, where as this requires much else to make it work. Also, the name 'retrace' doesn't suggest any flavor wins where as 'highstorm' IMO slightly does.

I agree that (combined) with retrace, this mechanic would look more sensible.

Brief discussion of it here: (((Parshendi Lightning)))

For a longer explanation: Highstorm came about because it is the defining feature of the planet in question -- huge storms with incredible destructive force that regularly scour the planet.

A mechanic with storm in the name clearly has to copy the spell it's on. Since regular storm is busted due to being uncapped, I designed this to be capped at one. That's all good.

Where it got difficult was the original cost to copy the spell. Originally, the cost was to sacrifice a land. That felt in flavor. However, it was potentially dangerous to encourage people to sacrifice the lands that they would need. So I changed it to exiling a land from your graveyard, with plans to have lots of enablers -- looting, a Fork in the Road style card, etc.

It's possible, however, that the switch, while mechanically superior, lost any sense of resonance. Maybe I should search for a better cost.

EDIT: Maybe "sacrifice a permanent"? Or it could just be normal storm but capped at one.

As for this card in particular, I was aware that it may be quite strong. I could see toning it down by removing one of the modes. And yeah, should probably use modal templating.

Actually, would making it modal work? I think if you copy a modal spell, the copy has the same mode as the original. So this would only target two permanents of the same type. Maybe I'll just drop it to a naturalize effect for balance and clarity.

How about using 'surge' instead? It encourages that 'storm like' playstyle to some extent.

Or something like, "copy this spell if you have cast another spell this turn"?

As far as copying goes, there's also this 'discipline', which I always liked.
http://www.mtgsalvation.com/forums/magic-fundamentals/custom-card-creation/366452-red-wedge-red-cards
It would obviously need to be reflavored though.

EDIT: For that dot in 'choose one' cards you can use this symbol/character: •