msem-instigator

Flying
Aedryd, Spectral Liege's power and toughness are each equal to the number of creatures you control.
{2}{W/U}: Another target creature you control gains flying until end of turn. When that creature leaves the battlefield this turn, create a 1/1 white Spirit creature token with flying.

Whenever Fireheart Centaur attacks, you may pay {2}{R}. If you do, it gets +1/+0 until end of turn for each Centaur you control.

Equipped creature gets +2/+2 and has poisonous 2. (Whenever this creature deals combat damage to a player, that player gets two poison counters.)
Whenever equipped creature attacks, create a 1/1 green Snake creature token with poisonous 1 that's tapped and attacking. Exile that token at end of combat.
Equip {2}

When Reconnaissance Expert enters, mill four cards.
When Reconnaissance Expert dies, return target noncreature permanent card from your graveyard to your hand.

Reach, deathtouch
Whenever you cast a spell from your graveyard, you may have Raven-Cursed Dominik fight target creature.

Spirited (When this creature enters, you may activate one of its activated abilities without paying its costs.)
{1}{R}, Discard a red card: Roggar deals 2 damage to any target. This damage can't be prevented.
{2}{R}, Exile a red card from your graveyard: Create two tapped 1/1 red Elemental creature tokens.

When Dewdrop Oracle enters, reveal the top four cards of your library. You may put a noncreature card from among them into your hand. Put the rest on the bottom of your library in any order.

[+1]: Tap up to one target creature. Azun, Sheriff of Daisite deals 1 damage to each opponent.
[–1]: Exile another target nonland permanent until Azun, Sheriff of Daisite leaves the battlefield.
[–7]: Detain each permanent target opponent controls. (Until your next turn, those permanents can't attack or block and their activated abilities can't be activated.)

Target player sacrifices a creature. Then you gain 3 life if that player doesn't control any creatures.

When Yamisaran Guard enters, create a colorless Equipment artifact token with “Equipped creature gets +1/+1” and equip {1}.

{T}: Add {C}.
{3}, {T}, Sacrifice Mystical Tomb: Return target artifact, enchantment, or legendary card from your graveyard to your hand.

Flash
When Artisan of Marrow enters, exile another target creature until Artisan of Marrow leaves the battlefield.

{T}: Add {C}.
{T}: Add {C}{C}. Spend this mana only to cast spells from your graveyard.

Double strike

At the beginning of your upkeep, you gain 1 life for each creature you control.
{3}{W}: Create a 1/1 white Soldier creature token. Activate only if you have the highest life total among all players.

Target creature gets +1/+1 until end of turn for each creature you control.
Inscribe {3}{R} ({3}{R}: 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.)

Sacrifice a creature: Pale Horse gets +2/+2 until end of turn.
Ride {B} ({B}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)

Flying
Whenever another creature dies, each opponent loses 1 life and you gain 1 life.

Creatures can't attack or block alone.

Target player sacrifices any number of lands. That player searches their library for up to that many land cards, puts them onto the battlefield tapped, then shuffles.
Fabled {5}{G}{G} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that player.)

Once each turn, when you activate a nonmana ability, you may tap target creature.
{1}{U}: Foggy Town Militia gains flying until end of turn.

Once each turn, when you sacrifice a permanent, you may put two progress counters on Ceaseless Research and surveil 2.
{2}{G}, Remove X progress counters from Ceaseless Research: Create an X/X green Mutant creature token. X can't be less than 3. Activate only as a sorcery.

{T}: Add {C}.
{T}, Tap an untapped creature you control: Add one mana of any color. You gain 1 life.

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.

Whenever Blood Constrictor becomes blocked by a creature, you gain life equal to that creature's toughness.