I only plan to have one spellbomb, since, well, Shalahd told you. I'm not sure what effect to go for, but I wanted something that didn't mess with the math like Giant Growth spellbomb would.

Also, is it me, or were the original spellbombs better? I know people would rather get an effect and draw a card, but the second generations weren't very clean, design-wise.

Why green for the only color? Is exiling it, rather than sacrificing it, purely for flavor?

Flavor. There's only so many left... they shouldn't be bouncing back from the graveyard.

No reason for green. Fog seemed like a workable spellbomb, but I could have cost it . Really, that first ability could be about anything.

Alright. I was just curious.

I agree that the first cycle of spellbombs were better designed than the second.

Why a limited supply? I would think that, given the flavour (single use then gone) that they would be among the first things a budding Artificer would learn to create. Did no artificers survive? Is there a specific component they no longer have access to?
It is a fine example of the spellbomb craft and I would play it if I drafted it and was playing green.

The idea here is that the Mirrans are having a hard time scavenging for parts... mostly because there's no metal in Glornica. The whole idea of a metal-low world is completely foreign to them... but that piece of the puzzle doesn't pop up on this flavor text. It does pop up on other cards, though.

From a mechanical point of view, though, I stuck with Fog for the exiling spellbomb because we're unlikely to see a Fog spellbomb otherwise. I don't know if you've ever played against Spore Frog.dec, but it is a very frustrating experience, once it gets going. I wouldn't want this card to be recurred over and over again.