msem-instigator

Menace
Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
Gilded Sell-Sword gets +2/+0 as long as you're in a renaissance.

Defender
Whenever Patient Cocoon is dealt damage, create a 1/1 green Insect creature token.

Flying, haste
Whenever you attack with three or more creatures, harmonize three times. (To harmonize, trigger up to one harmony of a permanent you control.)
If you would harmonize, you may instead return Herald of Festivities from your graveyard to your hand.

Civilized — This spell costs {1} less to cast if you control an artifact, a creature, and an enchantment.
Counter target spell.

Flying (This creature can't be blocked except by creatures with flying or reach.)
Vaporkin can block only creatures with flying.

Create a 1/1 blue Bird creature token with flying.
Inscribe {2}{U} ({2}{U}: Exile this card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)

Double strike, trample
Arise {3}{R}{W} ({3}{R}{W}, Exile this from your graveyard as a sorcery: Create a black token copy of it that's also a Zombie and can't block.)
When Bugrund arises, you may put an Equipment card from your hand or graveyard onto the battlefield attached to it.

Equipped creature gets +1/+1.
{1}: Equipped creature gains indestructible until end of turn. Sacrifice Focus Sash.
Equip {1}

You may have Snowfield Doppelganger enter as a copy of any creature on the battlefield, except it has “While a player is choosing targets as part of casting a spell, that player must choose at least one other creature that shares a name with this creature if able.”

[+1]: Creatures you control get +1/+0 and gain respawn until end of turn. (When one dies, if it attacked this turn, return it to its owner's hand.)
[0]: You get an emblem with “Whenever a creature you control attacks, you gain 1 life.”
[–5]: Until end of turn, Revela becomes a legendary Human Cleric Avatar creature with lifelink, indestructible, and “This creature's power and toughness are each equal to your life total.”

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Cycling {B} ({B}, Discard this card: Draw a card.)

Flying, haste
Whenever Warfury Dragon becomes enchanted or equipped, monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous.)

CySec Nexus enters tapped.
{T}: Add {W} or {U}.
{W}{U}, {T}: Create a Function token with “Flash.” Activate only as a sorcery. (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Counter target spell unless its controller pays {4}. 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.”)

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
{2}{W}{W}, Return an unblocked attacking creature you control to its owner's hand: Create a 4/4 white Angel creature token with flying that's tapped and attacking.

As Barren Desolation enters, you may pay 2 life. If you don't, Barren Desolation enters tapped.
{T}, Sacrifice Barren Desolation: Search your library for a Plains or Swamp card, put it onto the battlefield, then shuffle.

Flying
Demons and Vampires you control get +1/+1 for each player that has lost life this turn.

At the beginning of your end step, if Bramblemane didn't attack this turn, transform it.

(As an Encounter enters, choose an opponent to protect it. You and others can attack it. When defense counters are removed, create a 0/0 Army token if you don't control one, then put that many +1/+1 counters on a Army you control.)
When Settling of Nizev enters, look at the top four cards of an opponent's library, exile two of them, and put the rest on the bottom of their library in a random order. You may play those cards for as long as they remain exiled, and mana of any type can be spent to cast them.

I — Exile target creature an opponent controls until The Banishment of Seh'a leaves the battlefield.
II — Exile up to three cards from target opponent's graveyard.
III — You gain life equal to the number of cards in exile.

Swarming Midden enters tapped unless you control a basic Swamp.
{T}: Add {B}.
{1}{B}{B}: Swarming Midden becomes a 2/3 black Rat creature with menace until end of turn. It's still a land. Whenever it attacks this turn, create a 1/1 black Rat creature token with “This creature can't block.”

Whenever Forgotten King's Mask enters or equipped creature dies, attach it to target creature you control.
Equipped creature has base power and toughness 5/5 and is a Noble in addition to its other types.
{1}{R}, Discard two cards: Create a 1/1 white Human creature token and attach Forgotten King's Mask to it. Activate only as a sorcery.

{T}: Add {C}.
Satrapies you control have “{1}{G}, {T}: Put a +1/+1 counter on target creature. Activate only as a sorcery.”

Flying, haste

When Moonshadow Remnant enters, destroy target tapped creature.
Mirage {3}{W}{W} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)