Mistveil Plains

({T}: Add {W}.)
This land enters tapped.
{W}, {T}: Put target card from your graveyard on the bottom of your library. Activate only if you control two or more white permanents.

The List

Ultimate Masters

({T}: Add {W}.)
Mistveil Plains enters the battlefield tapped.
{W}, {T}: Put target card from your graveyard on the bottom of your library. Activate this ability only if you control two or more white permanents.

Shadowmoor

({T}: Add {W} to your mana pool.)
Mistveil Plains comes into play tapped.
{W}, {T}: Put target card in your graveyard on the bottom of your library. Play this ability only if you control two or more white permanents.

A land card that produces white mana, even a Plains, normally has no color.

Once you activate Mistveil Plains's last ability, it doesn't matter if you lose control of some of your white permanents.