Choose any number of creatures target player controls. Choose the same number of creatures another target player controls. Those players exchange control of those creatures. (This effect lasts indefinitely.)

You gain 2 life for each card in your graveyard.
Flashback (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Flying
, Discard a card: Return this creature to its owner's hand.

Whenever this creature deals combat damage to a creature, destroy that creature at end of combat.
Threshold — As long as there are seven or more cards in your graveyard, all creatures able to block this creature do so.

Create a 6/6 green Wurm creature token.
Flashback (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Flying, protection from each color

Flying
Whenever a creature dealt damage by this creature this turn dies, put a +1/+1 counter on this creature.
: This creature deals 1 damage to target creature.

Flying
Cognivore's power and toughness are each equal to the number of instant cards in all graveyards.

: This creature deals 1 damage to each creature without flying.

Volley of Boulders deals 6 damage divided as you choose among any number of targets.
Flashback (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Target player takes two extra turns after this one.