The mechanics feel much more like Fire in all honesty, like some explosive going off due to targeting. You could, of course consider it like Unstable Gas, but even Unstable Gas is a card that summons particular gases such that the input of Fire can explode them.
Might as well have this creature protect through some sort of explosions, a trap of fire. It would then make more sense and would probably be a more deserving new card to Fire's arsenal than even Seraph.
An explosive trap would probably also disable itself after it was triggered , and a trap in general seems more likely to conceal itself (
). My take Sky Guardian's theme is creates a windstorm around the target that the opponent that he has the option to go through or ignore.
Air can use the wind or other aerial effects as a method of disorientation or damage (Fog Shields are harnessed to intentionally disorient the enemy, Thunderstorms are directed to damage a certain area.). Sky Guardian expands upon this effect by harnessing the wind around it to create a force of 'protection' vs. opponents.
I appreciate the feedback though. Added a poll for the card's theme.