The List

Karoo

Karoo enters tapped.
When Karoo enters, sacrifice it unless you return an untapped Plains you control to its owner's hand.
{T}: Add {C}{W}.

Commander 2014

Karoo enters the battlefield tapped.
When Karoo enters the battlefield, sacrifice it unless you return an untapped Plains you control to its owner's hand.
{T}: Add {1}{W} to your mana pool.

Visions

Karoo comes into play tapped.
When Karoo comes into play, return an untapped plains you control to owner's hand or bury Karoo.
oc
T: Add o
W and one colorless mana to your mana pool.