Keyword: Threshold

Lightning Surge deals 4 damage to any target.
Threshold — If seven or more cards are in your graveyard, instead Lightning Surge deals 6 damage to that permanent or player and the damage can’t be prevented.
Flashback (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Flying
Threshold — As long as seven or more cards are in your graveyard, Fledgling Dragon gets +3/+3 and has “: Fledgling Dragon gets +1/+0 until end of turn.”

Flying
Whenever Treacherous Vampire attacks or blocks, sacrifice it unless you exile a card from your graveyard.
Threshold — As long as seven or more cards are in your graveyard, Treacherous Vampire gets +2/+2 and has “When Treacherous Vampire dies, you lose 6 life.”

Target nonblack creature gets -1/-1 until end of turn.
Threshold — If seven or more cards are in your graveyard, instead destroy that creature. It can’t be regenerated.

Threshold — Anurid Barkripper gets +2/+2 as long as seven or more cards are in your graveyard.

Threshold — Put three cards from your graveyard on the bottom of your library: Battlefield Scrounger gets +3/+3 until end of turn. Activate this ability only once each turn and only if seven or more cards are in your graveyard.

Threshold — As long as seven or more cards are in your graveyard, Treacherous Werewolf gets +2/+2 and has “When Treacherous Werewolf dies, you lose 4 life.”

Discard a card: Putrid Imp gains flying until end of turn.
Threshold — As long as seven or more cards are in your graveyard, Putrid Imp gets +1/+1 and can’t block.

Vigilance
Threshold — As long as seven or more cards are in your graveyard, Possessed Nomad gets +1/+1, is black, and has “, : Destroy target white creature.”

Destroy target land.
Threshold — If seven or more cards are in your graveyard, instead destroy that land and Rancid Earth deals 1 damage to each creature and each player.

Kamahl’s Sledge deals 4 damage to target creature.
Threshold — If seven or more cards are in your graveyard, instead Kamahl’s Sledge deals 4 damage to that creature and 4 damage to that creature’s controller.

Haste
Threshold — As long as seven or more cards are in your graveyard, Centaur Chieftain has “When Centaur Chieftain enters the battlefield, creatures you control get +1/+1 and gain trample until end of turn.”

Flying
Threshold — As long as seven or more cards are in your graveyard, Gloomdrifter has “When Gloomdrifter enters the battlefield, nonblack creatures get -2/-2 until end of turn.”

Threshold — As long as seven or more cards are in your graveyard, Pardic Arsonist has “When Pardic Arsonist enters the battlefield, it deals 3 damage to any target.”

, : Target creature gets -1/-1 until end of turn.
Threshold — , : Target creature gets -2/-2 until end of turn. Activate this ability only if seven or more cards are in your graveyard.

Trample
Threshold — As long as seven or more cards are in your graveyard, Possessed Centaur gets +1/+1, is black, and has “, : Destroy target green creature.”

Flying
Threshold — As long as seven or more cards are in your graveyard, Boneshard Slasher gets +2/+2 and has “When Boneshard Slasher becomes the target of a spell or ability, sacrifice it.”

Flying
Threshold — As long as seven or more cards are in your graveyard, Possessed Aven gets +1/+1, is black, and has “, : Destroy target blue creature.”

Flying
Threshold — As long as seven or more cards are in your graveyard, Mystic Familiar gets +1/+1 and has protection from black.

Destroy all enchantments.
Threshold — If seven or more cards are in your graveyard, instead destroy all enchantments, then return all cards in your graveyard destroyed this way to the battlefield.

Add .
Threshold — Add instead if seven or more cards are in your graveyard.

Protection from black
Threshold — Nantuko Blightcutter gets +1/+1 for each black permanent your opponents control as long as seven or more cards are in your graveyard.

Threshold — As long as seven or more cards are in your graveyard, Cephalid Sage has “When Cephalid Sage enters the battlefield, draw three cards, then discard two cards.”

Reach (This creature can block creatures with flying.)
Threshold — Seton’s Scout gets +2/+2 as long as seven or more cards are in your graveyard.

Vigilance
Threshold — As long as seven or more cards are in your graveyard, Reborn Hero has “When Reborn Hero dies, you may pay . If you do, return Reborn Hero to the battlefield under your control.”