msem-instigator

({T}: Add {G} or {W}.)
Whenever Resplendent Substratum becomes tapped, you lose 1 life unless you control two or more basic lands.

({T}: Add {W} or {U}.)
Rainsculpted Gorge enters tapped.
{1}, {T}: Add {W}{W} or {U}{U}.

Death knell — All creatures get -1/-1 until end of turn. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)
{B}, Sacrifice a creature: Choose a card in your graveyard with mana value less than the sacrificed creature's mana value. You may cast it without paying its mana cost.

Flying
Breach (Whenever this deals combat damage to a player, you may have it become an Aura Curse until your next turn. Attach it to that player.)
Whenever a cursed opponent draws a card, you may draw two cards.

Enchant artifact or creature
At the beginning of each upkeep, if enchanted permanent is tapped, untap it.
You control enchanted permanent.

Whenever a permanent you control transforms, draw a card.

Return all creature cards from your graveyard to the battlefield, then exile all but one of them.

If a source would deal damage to you or a permanent you control this turn, prevent all but 1 of that damage.
Metamorph {1}{W} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up and cast it at any time for its metamorph cost.)

Counter target spell.
Forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

Defiance (Whenever this creature takes damage, if it survives and wasn't defiant, put a +1/+1 counter on it and it becomes defiant.)
Each creature you control with a +1/+1 counter on it has lifelink.

Enchant creature
Enchanted creature gets +2/+2.
Sacrifice Steady Reminiscence: Enchanted creature gains indestructible until end of turn.

Distribute a vigilance, trample, first strike, and lifelink counter among up to four target creatures you control, then distribute four +1/+1 counters among those creatures.

Whenever a creature you control enters, if it wasn't cast, you gain life equal to that creature's toughness and may draw a card.
[+2]: Return up to one target creature card from your graveyard to the battlefield.
[–3]: Create an 8/8 blue Kraken creature token.
[–9]: Each player exiles all creature cards from their graveyard, then sacrifices each creature they control. Put each creature card exiled this way onto the battlefield under your control.

This spell costs {X} less to cast, where X is the power of the creature it targets.
Tyrant's Reckoning deals 4 damage to target creature.

This spell can't be countered.
Flying
Dominance — Whenever Stormwing Ultrateryx becomes the target of a spell an opponent controls, if you control the creature with the greatest power or tied for the greatest power, counter that spell.

When Rixia, Rift Shunted enters, target creature can't be blocked this turn.
Whenever a creature you control deals combat damage to an opponent, you may aetherize it. (To aetherize, create a token that's a copy of it, then exile that token.)

Voracious 2 (As this enters, you may sacrifice up to two artifacts and/or creatures. This creature enters with that many +1/+1 counters on it.)
When Hunted Wolf enters, create a 2/2 black Soldier creature token.

Menace
Whenever you cast a spell from anywhere other than your hand, each opponent discards a card if it's your turn. Otherwise, each opponent loses 2 life.

Exile target instant or sorcery spell you control. Until end of turn, you may cast that card from exile without paying its mana cost. When you do, copy it. You may choose new targets for the copy.

Target creature gets -2/-1 and gains winnow until end of turn. (Damage dealt to it also causes its controller to lose that much life.)

{T}: Add {G} or {W}. You lose 1 life unless you have less life than an opponent.

Flying
When Ancient of Reflections enters, create a token that's a copy of target creature you control not named Ancient of Reflections, except it's 1/1 and has haste. Sacrifice it at end of turn.

When Journeying Packmaster enters, look at the top card of your library. If it's a land card, you may put it onto the battlefield tapped. If you didn't put that card onto the battlefield, draw a card.

When Sun-Blessed Hoplite enters, target creature you control gets +X/+X until end of turn, where X is your devotion to white. (Each {W} in the mana costs of permanents you control counts toward your devotion to white.)

Motivate 2 (When this creature enters, you may motivate target creature with less power than this by putting two +1/+1 counters on it.)
Each creature you control with a +1/+1 counter on it has trample.