Saphia, Throne Taker

Creatures you control that are owned by another player have lifelink.
At the beginning of each opponents end step, if
that player controls more than three creatures
you may pay X life. If you do, take control of
target creature that player control with a
converted mana cost of X.
At the start of your upkeep, if you control more creatures than any opponent, you become the
monarch.