msem-instigator

Search your library for a creature card, reveal it, put it into your hand, then shuffle. Then if you control a creature with power 4 or greater, you may pay {4}. If you do, you may put a creature card from your hand onto the battlefield.

Mimic—Discard a card (Discard a card as a sorcery: This takes the shape of your choice.) [1/1]
[Shape 1] Menace
Soulshifter gets +1/+1 for each creature card in your graveyard. [1/1]
[Shape 2] Deathtouch
Whenever Soulshifter deals combat damage to a player, you may return target creature card from your graveyard to your hand. [2/2]

When Street Stalker enters, target opponent loses 1 life for each creature you control named Street Stalker.

Scry 2, then draw two cards. You lose 2 life.

Destroy target attacking or blocking creature.

Ominous Dragoncaller gets +1/+1 and has flying as long as you control a Dragon.

Valdez's Strike Leader can't be blocked if you have more cards in hand than defending player.

As an additional cost to cast Acid Sewage, reappropriate or pay {3}. (To reappropriate, exile exactly two cards from your hand and/or graveyard.)
Destroy target creature.

Double strike

Art of war — At the beginning of your end step, if Kuryu Swordsman dealt damage to an opponent this turn, you may have Kuryu Swordsman fight target creature you don't control. (Each deals damage equal to its power to the other.)

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
{2}{G}{W}: Create an Idol token. Prevent all damage that would be dealt to and dealt by target creature this turn.
At the beginning of your end step, if you're in a renaissance and you control ten or more Idols, you win the game.

Flying
Whenever Cavern Scourge attacks, you may exile a card from your graveyard. If you do, you gain 3 life.

Flying
Whenever an opponent casts a spell, copy it. You may choose new targets for the copy.

As long as you control no other Humans, Lone Survivor gets +2/+2 and has “Noncreature spells cost {1} more to cast.”

Deathtouch
Whenever another creature named Winter's Whelp you control enters, you draw a card and you lose 1 life.

Defender
{T}: Scale-Crown Archer deals 1 damage to each opponent.
Prismatic — Whenever you cast a multicolored spell, untap Scale-Crown Archer.

Destroy all monocolored creatures.

Creatures you control get +2/+2 until end of turn.
Leitmotif (If you cast this spell from your hand, exile it as it resolves. When you next cast a spell that shares a color with this card, you may cast this from exile without paying its mana cost.)

Whenever a land you control enters or a land card is put into your graveyard from anywhere, create a 0/1 green Plant creature token.
{3}{G}{G}: Put a +1/+1 counter on each other creature you control.

{R}{W}{B}, Discard a card named Ni'Ama, God of Adversity: Ni'Ama gains indestructible and becomes a God creature in addition to its other types.
Whenever Ni'Ama enters or attacks, it deals 2 damage to each opponent unless they discard a card. You gain that much life. Repeat this process once.

Sacrifice Masahita's Servant: Exile the top card of your library. Until end of turn, you may play that card.

Haste
When Challenging Pupil enters, conjure a card named Fatigue and put it on top of your library. (It's a colorless sorcery that costs {2} with “Draw a card.”)

Create two 2/1 black and red Cat Pirate creature tokens with menace. You lose 2 life.

Trample, haste
Whenever an opponent casts a noncreature spell, you may return Olten Sandwurm to its owner's hand.

Flying, deathtouch