Herald of Doomsday

When Herald of Doomsday enters the battlefield, search your library for a card named Doomsday,
put it into your hand, shuffle your library, then discard your hand.
At the beginning of your end step, your life total
becomes equal to the number of cards in your
hand.
{p/u}{p/r}: Change the target of a spell or ability that
only has a single target. Activate only during an opponents turn.