msem-instigator

Whenever Scavenger of the Old Bay deals combat damage to a player, draw a card.
Ride {1}{U} ({1}{U}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

Flying, deathtouch
{B}: Emissary of Dreaded Night gets +1/+1 until end of turn. Activate only if Emissary of Dreaded Night is embattled. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Sky-High Spires enters tapped unless you have two or more opponents.
{T}: Add {W} or {U}.

Choose target player, then choose two —
• That player loses 2 life.
• That player draws two cards.
• Put two -1/-1 counters on target creature that player controls.

Choose one —
• Target creature gets +3/+0 until end of turn.
• Destroy target artifact.

Reach (This creature can block creatures with flying.)
Whenever a land you control enters, Rammanethi Sandshaper deals 1 damage to target creature with flying.

Alpha (You may have this creature enter with a +1/+1 counter on it. If you do, it becomes alpha and can only attack alone.)
Vigilance

Runescale Brawler enters with three +1/+1 counters on it.
If damage would be dealt to Runescale Brawler while it has a +1/+1 counter on it, prevent that damage and remove a +1/+1 counter from Runescale Brawler.

Reach
Towering Silkweaver can block an additional creature each combat.

Flying, trample
Once during each of your turns, you may cast a spell from your graveyard without paying its mana cost.
When Yhzag, Alpha and Omega is put into a graveyard from anywhere, its owner shuffles their graveyard into their library.

Your opponents play with their hands revealed.
Whenever you cast a spell with the same name as a card in an opponent's hand, draw two cards.

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)

Destroy target creature if it has the least power or is tied for least power among creatures on the battlefield.
Memento {3}{B}{B} (You may cast this from your graveyard for {3}{B}{B}. If you do, put it onto the battlefield transformed after it resolves. Exile it if it would leave the battlefield or not resolve.)

Flying
Whenever you cast a noncreature spell, create a 1/1 blue Faerie Rogue creature token with flying.
Whenever one or more creature tokens you control deal combat damage to a player, you may pay {G/U}. If you do, draw a card.

Whenever you cast an instant or sorcery spell, target creature can't block this turn.

Whenever another creature you control enters, Sunblessed Orator deals 1 damage to each opponent and you gain 1 life.

Art of war — At the beginning of your end step, if Exultant Oni dealt damage to an opponent this turn, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)

If two or more creatures an opponent controls are attacking, you may pay {B} rather than this spell's mana cost.
Create a 1/1 black Snake creature token with deathtouch. It gains first strike until end of turn.

{1}, Sacrifice Gasoline Canister: It deals 1 damage to any target. If a creature or planeswalker dealt damage this way would die this turn, exile it instead.

Enchant opponent
You control enchanted player except during their extra turns.
At the beginning of enchanted player's end step, if it isn't an extra turn, they take an extra turn after this one.

Flying, hexproof, haste
Blue permanents you control have hexproof.
Whenever you activate an ability of a red permanent, you may copy that ability. If you do, choose new targets for the copy.

Equipped creature has “Whenever this creature attacks, untap each other creature you control.”
Equip {3}

Reveal the top four cards of your library. You may put a creature card and/or a land card from among them into your hand. Put the rest into your graveyard.

Whenever Greenscale Bully deals combat damage to a player, create a Treasure token. (It's an artifact with “{T}, Sacrifice this permanent: Add one mana of any color.”)

Prismatic Cavern enters tapped.
When Prismatic Cavern enters, return a land you control to its owner's hand.
{T}: Add {C} and one mana of any color.