This is the Fire Fly HS Card from the Journey to Un’Goro expansion due for release in April.
It’s a Neutral minion and the card reads: Battlecry: Add a 1/2 Elemental to your hand.
You can get Fire Flyby opening packs from the Journey to Un’Goro set.
*A cheap Elemental to activate some of the other Elemental synergy cards that are being released.