msem-instigator

Target creature gets +2/+2 until end of turn. If it's an enchanted creature or enchantment creature, it also gains hexproof and indestructible until end of turn. (It can't be the target of spells or abilities your opponents control. Damage and effects that say “destroy” don't destroy it.)

Other creatures you control can't attack or block alone.

{1}{R}: Aravant Throatcutter and up to one other target Pirate or Rogue you control each get +1/+0 until end of turn.

Equipped creature gets +1/+0.
Whenever equipped creature attacks, you may draw a card then discard a card.
Equip {2}

Target creature you control gets +2/+2 until end of turn. If it's attacking, 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.”)

Target creature gains double strike until end of turn.

Trample
Arpechian Champion can only attack or block alone.
Whenever a land you control enters, put a +1/+1 counter on Arpechian Champion.

Enchant land
When Arrive, Surrounded by Petals enters, audition for green. (Create a 1/1 Construct Actor creature token, a Scout Role giving 2/3 and vigilance, or a Warrior Role giving 3/2 and trample. Roles replace older ones.)
Enchanted land has “{T}: Add one mana of any color.”

Target creature gets +1/+1 until end of turn. Untap that creature.
Fabled {2}{W} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that creature.)

Winnow (Damage dealt to this creature also causes you to lose that much life.)
{2}{B}: Each creature blocking Arroyo's Servant gains winnow until end of turn.

Flying
Improve {1}{U} ({1}{U}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)

Hexproof
At the beginning of your upkeep, put a card from your hand on top of your library. You may shuffle.
{1}: Look at the top three cards of your library, then put them back in any order.
{2}{U}: Draw a card.

The next time target creature would be dealt damage this turn, prevent all but 1 of that damage. Whenever that creature perseveres this turn, put a +1/+1 counter on it. (A creature perseveres when it survives damage.)

Creatures you control get +1/+1 until end of turn. You gain 3 life.
Memento {4}{W}{W} (You may cast this from your graveyard for {4}{W}{W}. If you do, put it onto the battlefield transformed after it resolves. Exile it if it would leave the battlefield or not resolve.)

{B}: Remove a counter from target permanent.
{3}{B}: Move a counter from target permanent onto Ashfeaster Ghouls. Ashfeaster Ghouls can't be blocked this turn.

Gestalt (When this or another creature enters under your control, you may merge it with the one in play, keeping counters and attachments. They become the permanent on top plus all abilities from under it.)
This creature can't be sacrificed.

Haste
{T}, Sacrifice a creature: Ashspeaker deals 1 damage to any target.

When Asking Imp enters, an opponent may pay 2 life. If they do, return Asking Imp to its owner's hand.

Aspiring Dragon has flying and haste as long as you control another Dragon.
{2}{R}{R}: Aspiring Dragon gets +3/+0 until end of turn.

Whenever Aspiring Hero attacks alone, put a +1/+1 counter on it.
When Aspiring Hero dies, each opponent gains life equal to its power.

Vanguard — Whenever a creature you control attacks alone, it gets +1/+1 until end of turn.

Put a +1/+1 counter on target attacking creature.
Draw a card.

When you discard Attack Vector, you may cast it from your graveyard.
Exile the top two cards of your library. Until the end of your next turn, you may play one of those cards.

Enchant creature
As long as you control an untapped creature, enchanted creature can't attack or block.

Sacrifice a creature: Exile the top card of your library. Until end of turn, you may play that card.