Maiden Astraea

As long as your tendency is white, other creatures you control get +0/+1 and have lifelink.

As long as your tendency is black, other creatures you control get +1/+0 and have wither.

When you control no other creatures, sacrifice Maiden Astraea.
"Leave us, Slayer of Demons. This is a sanctuary for the lost and wretched. There is nothing here for you to pillage or plunder" - Maiden Astraea