[shatner]

Really, I don't think anyone is arguing that giving the Zmey cold-blooded would make it's defeat likely in a cold province. I think the larger question is whether the Zmey having that weakness is too much.

The point is the Zmey is an extraordinary raiding unit which skirts the line between heavy thug and SC. It flies, has three lives, very high protection, does AoE fire damage on top of 4 high strength attacks (so one is likely to connect even when the foe is ethereal AND fire immune). The Zmey being a poor choice to invade a cold nation is fine. After all, you know not to rely on body ethereal to protect your SC against Caelum when even their PD has magical ice weaponry. That's the tactics of the game. And having the correct response to a Zmey be Wolven Winter combined with a remote attack spell sounds like a gem and research-appropriate counter.

Finally, fire gems suffer from fewer viable outlets than other gem-types. The main uses for fire gems are forging fire-spam items, lightless lanterns or used as an ingredient for non-fire gear (firebrands, gold shields, rune breakers, etc.). That makes saving up for an awesome summon like the Zmey a very easy decision to make. If the Zmey cost death gems or earth gems instead, I'd be more hesitant to weaken it, but not fire gems.

I think the change is both thematically appropriate and mechanically balanced.