Galakrond's Awakening Adventure Guide & Card List
For the rest of the game,your Hero Power can target minions.
It's an arena-only spell that will appear as an option during the draft for a limited time.
From Hearthstone Wiki:
Deadeye is unique to the Arena and can only be obtained via drafting it during an Arena game.
Deadeye is uncraftable and cannot be crafted or be obtained from card packs.