Wild Pair

Whenever a creature enters, if you cast it from your hand, you may search your library for a creature card with the same total power and toughness, put it onto the battlefield, then shuffle.

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Conspiracy: Take the Crown

Whenever a creature enters the battlefield, if you cast it from your hand, you may search your library for a creature card with the same total power and toughness and put it onto the battlefield. If you do, shuffle your library.

Premium Deck Series: Slivers

Whenever a creature enters the battlefield, if you cast it from your hand, you may search your library for a creature card with the same total power and toughness, put it onto the battlefield, then shuffle your library.

Planar Chaos

Whenever a creature comes into play, if you played it from your hand, you may search your library for a creature card with the same total power and toughness and put it into play. If you do, shuffle your library.

If the creature that entered has left the battlefield by the time the ability resolves, use the power and toughness of that creature as it last appeared before leaving the battlefield.

If you cast a 2/2 Grizzly Bears, for example, you may then search for any creature with total power and toughness 4. It can be 0/4, 1/3, 2/2, or 3/1.

The game checks the power and toughness of the creature that just entered as it exists on the battlefield. That might mean it's impossible to get another copy of that same card. For example, a Triskelion on the battlefield is 4/4, but a Triskelion in your library is 1/1. The power and toughness might also have been affected while the triggered ability was on the stack (such as with Giant Growth, Sudden Death, or Ovinize).