Destroy all creatures. They can't be regenerated.
Threshold — If there are seven or more cards in your graveyard, instead destroy all creatures, then create two 1/1 white Spirit creature tokens with flying. Creatures destroyed this way can't be regenerated.

Flying, protection from each color

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

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.

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.

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

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

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.

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.