Pretty darn nifty! I’ve always been a sucker for Vespyr decks, and this looks like a great 5 drop for the deck. The buff works especially well with Voice of the Wind, Snowchaser, and Bonechill Barrier. However, at 5 mana, there is so much that Vespyr vanar wants to play, such as Frostburn, Luminous Charge, Vesperian Might, and Frostiva. I can see this being insane in Vespyr based aggro or swarm tactics, and the fact that it is an artifact adds a new dimension to its counterplay.
Between this and Drauger Eyolithe, I can see a position-based midranged Vespyr Vanar beginning to develop.