The Sisters of Twilight

Loyal Mount {2}{g} (You may pay an additional {2}{g} as you cast this spell)
Double strike, forestwalk, reach
When this creature enters the battlefield, if you
paid its Loyal Mount cost, choose one —
•Search your library for Gwindalor, King
Descendant and put it onto the battlefield.
•Search your library for Ceithin-Har, Woe
Dragon and put it onto the battlefield.