msem-instigator

Multipurpose Mannequin gets +1/+1 for each permanent attached to it.

Menace
Whenever an opponent discards a card, monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous.)

Enchant player
Whenever enchanted player is attacked, the attacking player creates a tapped and attacking token that's a copy of an attacking creature of their choice, except it's not legendary and has “This permanent can't transform.” That token's controller sacrifices it at end of combat.

Protection from instants and from sorceries
At the beginning of your upkeep, sacrifice another creature. If you do, put a +1/+1 counter on Andazir, the Crownless.
At the beginning of your end step, if you control four or fewer creatures, transform Andazir.

When Whisperwoods Reclaimer enters, if there are three or more land cards in your graveyard, return target land card from your graveyard to the battlefield tapped.

Scornful Flames deals 4 damage to target player.
Dominance — Scornful Flames deals 1 damage to each creature that player controls if you control the creature with the greatest power or tied for the greatest power.

When Leafdown Lookout enters, if you control another Scout, draw a card, then you may put a land card from your hand onto the battlefield tapped.

Electrical Eradication deals 3 damage to each nonlegendary creature. Then if you controlled a red legendary creature or planeswalker as you cast this spell, it deals 3 damage to each nonlegendary creature and each opponent.

Flying
If a source without flying would deal damage to you, prevent 2 of that damage.
Crew 5

Create a Treasure token.
Showcase {2}{R} (Then if you cast this for its showcase cost, create a 1/1 red Bard creature token that can't block and exile this. Whenever it attacks, you may cast a free copy of this.)

({T}: Add {B}.)
Moon of the Encroaching Night enters tapped.
{1}{B}, {T}: Scry 1.

Ward {2}
When Rewriter of Flesh enters, target creature you control becomes an enchantment and loses all other card types. (It still has its abilities, but it's no longer a creature.)

You get a fuse counter, then Ignition Sequence deals X damage to any target, where X is 2 plus the number of fuse counters you have.

Legacy (You may play this side of this card only from your graveyard. Exile it if it would leave the battlefield or not resolve.)
Whenever a Warrior you control becomes the target of a spell or ability an opponent controls, that player loses 1 life and discards a card, then you draw a card and gain 1 life.

Vivid Creek enters tapped with two charge counters on it.
{T}: Add {U}.
{T}, Remove a charge counter from Vivid Creek: Add one mana of any color.

Whenever another creature you control enters, target opponent loses 1 life and you gain 1 life.
Sacrifice Somber River Bearer: Creatures you control gain indestructible until end of turn.

Target player reveals their hand. You choose a nonland card from it. That player discards that card.(Cast a copy of this spell once while this creature is on the battlefield.)

Whenever one or more other nontoken creatures die, create a Food token. (It's an artifact with “{2}, {T}, Sacrifice this artifact: You gain 3 life.”)
Whenever you sacrifice a Food, create a 1/1 black Bat creature token with flying.

At the beginning of combat on your turn, you may exile an instant or sorcery card from your graveyard. If you do, another target Pirate or Rogue gains flying until end of turn.

Whenever Sandbluff Inciter attacks, it deals damage to defending player equal to the number of tapped creatures you control.

When Consumption Catalyst enters, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
Whenever you draw a card, each opponent loses 1 life and you gain 1 life.

Trample
Harmony — Avalanche Drummer deals 1 damage to any target.
When Avalanche Drummer enters, harmonize. (Trigger up to one harmony of a permanent you control.)

Until end of turn, target creature gets +1/+0 and gains “Whenever this creature is dealt damage, exile that many cards from the top of your library. Until end of turn, you may play those cards.”

Flying
Whenever you attack with three or more creatures, exile the top card of your library. You may play that card until you exile another card with Zarthane, Scourge of Galdurheim.
{2}{B/R}: Target creature gets +1/+0 and gains menace until end of turn. Activate only as a sorcery.

Vigilance, trample
Prized Marshcroaker can block an additional creature each combat.