Zephyr Sprite
A one-mana 1/1 flyer is the most basic unit a blue tempo deck can buy: a body that gets in for a point and can carry whatever you attach to it. That is the entire pitch, and it has been the same pitch since Flying Men set the template for blue evasion at the lowest possible cost. Zephyr Sprite is that template wearing a creature type, slotting the same stat line into the Faerie tribe rather than an ordinary humanoid. The body asks nothing of the rest of the deck and offers nothing back beyond the swing, which is exactly what unconditional filler is built to do: fill a specific shape, an evasive one-drop for a tribe and a tempo plan that want bodies in the air immediately. The Faerie line is the only thing that distinguishes it from a dozen functionally identical printings, and in environments where that line matters, the distinction is the whole reason to run it over the alternatives.
