msem-instigator

Rather than pay the mana cost for a spell, its controller may discard a card that shares a color with that spell.
Whenever an opponent casts a spell, counter that spell unless they pay 5 life.

Whenever you cast a noncreature spell, any number of target creatures you control get +1/+1 until end of turn.
Whenever a creature you control deals an amount of combat damage exactly equal to its mana value to a player or planeswalker, draw a card.

Flying
Whenever you tap a land for mana, add one mana of any type that land produced.
At the beginning of each end step, if you control no untapped lands, transform Martoob, Blessing of Water.

Target player loses 3 life and you gain 3 life. (Then exile this card. You may cast the creature later from exile.)

Whenever you cast a noncreature spell, Hutao's Wardens deals 2 damage to each opponent. Then if that spell was an enchantment, scry 2.

Prowess
{1}{U}, Tap an untapped Wizard you control: Target creature gets -3/-0 until end of turn.

Draw a card.
If this is the second spell you cast this turn, scry 2. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

Flying, trample, haste
{W}{U}{B}{R}{G}: Create a token that's a copy of another target creature except it's all colors and has haste.
{W}{U}{B}{R}{G}, Exile Soul of Iscathia from your graveyard: Create a token that's a copy of target creature except it's all colors and has haste.

Put a divinity counter on target creature. It gains “This creature has indestructible as long as it has divinity counter on it.” (This effect lasts indefinitely.)

Each player loses 3 life, then discards a card, then sacrifices a creature, an enchantment, a land, a planeswalker and a token. Then exile all graveyards.

Target player reveals their hand. You choose a nonland card from it. That player discards that card. 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.”)

Flying
Whenever Olson's Armada attacks, if only one creature crewed it, create a 1/1 white Bird creature token with flying. Otherwise, put a +1/+1 counter on Olson's Armada.
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

Defender, flying
Ruins Guardian can attack as though it didn't have defender as long as a creature died under your control this turn.
Whenever Ruins Guardian attacks, you may exile two creature cards from your graveyard. If you do, draw a card.

[+2]: Create a 2/2 red Werewolf creature token with first strike and haste.
[–3]: Tanya deals 3 damage to each creature that's not a Wolf or a Werewolf.
[–8]: For each permanent your opponents control, that player sacrifices it unless they have Tanya deal 2 damage to them.

Look at the top card of your library. You may put it into your graveyard. Repeat this process twice, then draw a card.

Up to one target creature gets -2/-2 until end of turn. Put a +1/+1 counter on up to one target creature you control.

Ward—Pay 3 life and discard a card.
Once each turn, when another creature leaves the battlefield, you may have target creature become a copy of that creature until end of turn.

Advance {5}{B}{B} (Cast this for {5}{B}{B} to advance it as it enters. {5}{B}{B}: Advance this as a sorcery.)
Whenever Sluiceway Collector advances, put a permanent card from a graveyard onto the battlefield under your control.

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.)

Whenever Daring Skythief crews a Vehicle, that Vehicle gains flying until end of turn.

Whenever you foretell a card or cast a foretold spell, Bugrund's Schemer deals 2 damage to each opponent.

Enchant creature
Enchanted creature gets +1/+0 and has haste.
Once each turn, when enchanted creature becomes tapped, you may add {R}{R}. Until end of turn, you don't lose this mana as steps and phases end.

Equipped creature gets +2/+2 and has lifelink and vigilance.
Equip Angel {2}
Equip {5}

When Liturgy of Brine enters, draw a card, then you may put a land card from your hand onto the battlefield tapped.
Invocation — Whenever you spend four or more mana to cast a spell or activate an ability during your turn, Liturgy of Brine becomes a 5/5 Kraken Horror creature in addition to its other types until end of turn.