Volatile Stormdrake can trade its small flying body for a much more useful opposing creature. Its entry trigger exchanges control with a targeted creature an opponent controls, then gives you four energy. You must spend energy equal to the acquired creature's mana value or sacrifice it, so the outcome depends on both the target and your energy reserve.
With no existing energy, a creature costing four or less can usually be kept using the energy supplied by the trigger. A more expensive creature can still be removed through the exchange and sacrifice, although the opponent receives your Stormdrake. Extra energy from other cards expands the range of creatures you can retain.
The exchange needs both creatures available for a legal exchange as the ability resolves. Removing the Stormdrake before resolution can prevent the intended swap. Its hexproof from activated and triggered abilities helps against some interaction, but spells can still target it. That protection also does not make the opposing target automatically legal.
Blink decks can use repeated entries to find new exchange opportunities, but ownership and control deserve attention when the Drake has changed sides. In a straightforward blue deck, the card offers a cheap way to take a useful creature or convert a large threat into a smaller opposing flyer. Choose based on the actual board: taking a modest value creature permanently can be better than spending the card merely to force an expensive creature into the graveyard.
