Corrupting famine

•This land enters the battlefield tapped. On your upkeep, change one non swamp basic land to a swamp.
•{t}: add one {b} mana
•{b}{b}{b}{b},{t}: Target player gains control of this card, or exile this card
{bull}When this card is destroyed you can sacrifice one swamp to return it to the battlefield under target players control, or you must exile this card
{bull}all cards turned to swamps by this card return to normal when this card is exiled