msem-instigator

Marrowskitter can't block and can't be blocked.
{3}{B}{B}: Return Marrowskitter from your graveyard to the battlefield. Create a token that's a copy of it.

{T}, Reveal an Angel card from your hand: For each of that card's colors, add one mana of that color.

Flying, ward {2}
The first noncreature spell you cast each turn costs {X} less to cast, where X is your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Colorless creatures you control get +1/+1.

Exile target nonland permanent. You lose 3 life.

Haste
When Qilan Stormers enters, it gets +X/+0 until end of turn, where X is the number of creatures you control.

{W}{B}, Shuffle Inexorable Explorer into your library: Return target creature card from your graveyard to the battlefield.
{W}{B}, Sacrifice a creature: Return Inexorable Explorer from your graveyard to the battlefield tapped.

{T}: Add {C}.
{3}{R}: Until end of turn, Defect's Precinct becomes a 3/3 creature. It's still a land. It has trample if {G} was spent to activate this ability, has vigilance if {W} was spent, and has hexproof if {U} was spent.

Flash
Wanderlust — When Microzoologist enters, search your library for a creature card with mana value 1. If you control four or more differently named lands, you may search for a creature card with mana value 3 or less instead. Reveal that card, put it into your hand, then shuffle.

Return target creature card from your graveyard to your hand. If that card is a Human, you gain 3 life.
Flashback {3}{W} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Haste
When Wretched Merfolk enters, target creature can't block this turn.

Improve {W} ({W}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
Whenever one or more embattled creatures you control attack, create a 1/1 white Cleric creature token with lifelink. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Trample
{4}{R}{R}: Tortle Tinkerer explores. This ability costs {1} less to activate for each artifact you control. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then you may put that card in your graveyard.)

Flash
Flying
When Mending Valkyrie enters, choose target permanent you own or permanent card with mana value 3 or less in your graveyard. You may return it to your hand.

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

Reveal the top four cards of your library. You may put a permanent card revealed this way with mana value less than the greatest mana value among permanents you control onto the battlefield. Put the rest on the bottom of your library in a random order.

Barren Boneyard enters tapped.
{T}: Add {B}.
{2/B}{2/B}: Barren Boneyard becomes a 2/3 black Elemental creature with deathtouch until end of turn. It's still a land.

Whenever you gain life, draw a card. This ability triggers only once each turn.
{6}: Angelic Statue becomes a 3/3 white Angel creature with flying and lifelink until end of turn.

Reach, trample
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
Whenever one or more tokens you control enter, put a +1/+1 counter on Harvesttide Nemesis. This ability triggers only once each turn.

At the beginning of your upkeep, you may pay {1}{G/U}. If you do, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)
At the beginning of your end step, you may pay {1}{G/U}. If you do, populate. (Create a token that's a copy of a creature token you control.)

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever you cast a noncreature spell, target creature can't block this turn.

Festive Servitor gets +1/+1 for each color among spells you've cast this turn.
{2}: Add one mana of any color.

When Lotus Debutante enters, create a colorless artifact token named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”
{3}{U}: Draw a card.

First strike
Whenever a nontoken creature you control leaves the battlefield, you may pay {W}. If you do, create a 1/1 colorless Spirit creature token.

Vigilance
Cat creatures you control have vigilance.
When Savannah Scout enters, create a 2/2 white Cat creature token.