Target creature gets +X/+X until end of turn, where X is your devotion to green. (Each in the mana costs of permanents you control counts toward your devotion to green.)
(15/09/2013)
Hybrid mana symbols, monocolored hybrid mana symbols, and Phyrexian mana symbols do count toward your devotion to their color(s).
(15/09/2013)
Numeric mana symbols (, , and so on) in mana costs of permanents you control don’t count toward your devotion to any color.
(01/02/2014)
The value of X is calculated as Aspect of Hydra resolves. The bonus won’t change later in the turn, even if your devotion to green does.
(15/09/2013)
If an activated ability or triggered ability has an effect that depends on your devotion to a color, you count the number of mana symbols of that color among the mana costs of permanents you control as the ability resolves. The permanent with that ability will be counted if it’s still on the battlefield at that time.
(15/09/2013)
Mana symbols in the text boxes of permanents you control don’t count toward your devotion to any color.
