Regal Behemoth

Trample
When this creature enters, you become the monarch.
Whenever you tap a land for mana while you're the monarch, add an additional one mana of any color.

Utopia Sprawl

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

Harmonize

Radha, Heir to Keld

Whenever Radha attacks, you may add {R}{R}.
{T}: Add {G}.

Boreal Druid

Elvish Mystic

Arbor Elf

Wild Growth

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