Khalni Hydra

This spell costs {G} less to cast for each green creature you control.
Trample

Utopia Sprawl

Enchant Forest
As Utopia Sprawl enters, choose a color.
Whenever enchanted Forest is tapped for mana, its controller adds an additional one mana of the chosen color.

Fyndhorn Elves

Elvish Mystic

Yavimaya, Cradle of Growth

Each land is a Forest in addition to its other land types.

Wild Growth

Enchant land
Whenever enchanted land is tapped for mana, its controller adds an additional {G}.

Primalcrux

Trample
Chroma — Primalcrux's power and toughness are each equal to the number of green mana symbols in the mana costs of permanents you control.