Agata, Patron of the Wild

Companion — Each land in your starting deck is
basic. (If this card is your chosen companion, you
may cast it once from outside the game.)
When you cast Agata, Patron of the Wild, choose
a color, then choose target land.
Whenever the chosen land is tapped for mana, its controller adds two additional mana of the chosen
color. (In addition to the mana the land produces.)