msem-instigator

Colossal 3—{5}{U} (You may cast this for its colossal cost to have it enter with three +1/+1 counters; or pay {5}{U} as a sorcery: Put three +1/+1 counters on it if it has none.)
When Omendiver's colossal ability puts one or more counters on it, scry 3.

Flying, trample
Whenever Skali, the Last Sunfeather attacks, abound. If a creature spell is cast this way, you may have that creature enter tapped and attacking. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)

When Evanescier Greypelt enters, it fights target creature.
Mirage {3}{G} (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.)

Exile target artifact or enchantment. You gain 1 life.

Chronicle (As this enters and after your draw step, add a lore counter. Stop after III.)
[Lore I-II] You may discard a card. If you do, draw a card.
[Lore III] Create a token that's a copy of another target creature you control, except it has haste. Sacrifice it at the beginning of the next end step.

You may have Graveborn Usurper enter as a copy of any creature card in a graveyard, except it has “{2}{U}{B}, Exile a creature card from a graveyard: Graveborn Usurper becomes a copy of the exiled card, except it has this ability.”

Glitch {1} (Remove one [restriction] for each time you pay the glitch cost.)
Target opponent reveals their hand. You choose a [noncreature,] nonland card [with mana value 3 or less] from among them. That player discards that card.

You may have Fleeting Memory enter as a copy of any creature on the battlefield, except it has “At the beginning of the end step, exile this creature.”

Sacrifice Repurposed Killdrone: It deals 1 damage to any target. You gain 1 life.

Concord — When Palace Servant enters, if there are four or more card types among permanents you control, create two 1/1 white Merfolk creature tokens.

You may cast a spell with mana value 3 or less from your hand without paying its mana cost. (Then exile this card. You may cast the creature later from exile.)

Whenever a creature with a counter on it dies, create a Gold token. (It's an artifact with “Sacrifice this artifact: Add one mana of any color.”)

({T}: Add {W} or {U}.)
As Lakeside Park enters, you may pay {1}. If you don't, Lakeside Park enters tapped.

When Crinster Tattooist enters, put a +1/+1 counter on each tapped creature you control.

Colossal 2—{4}{G} (You may cast this for its colossal cost to have it enter with two +1/+1 counters; or pay {4}{G} as a sorcery: Put two +1/+1 counters on it if it has none.)
Reach

When Entelan Savant enters, scry 2.

Ward—Exile three cards from your graveyard. (Whenever this permanent becomes the target of a spell or ability an opponent controls, counter it unless that player exiles three cards from their graveyard.)
Menagerie — Astralhorn Familiar gets +2/+2 as long as there are five or more creature types among creatures you control.

{T}: Add {C}.
{5}, {T}, Sacrifice Wildkin Grove: Create three 1/1 colorless Shapeshifter creature tokens with changeling. (They're every creature type.)

{U}: Primordial Manifestation gets +1/-1 until end of turn.
Whenever Primordial Manifestation deals combat damage to a player, draw a card.

{T}: Add {C}.
{1}, {T}: Add {W}{B}.

{2}, {T}, Sacrifice Tunnel Map: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Flying, lifelink

At the beginning of your upkeep, exile the top card of your library. If a land card is exiled this way, add {R}{R}. You don't lose this mana as steps and phases end this turn. Otherwise, you may cast that card this turn.

Flash
This spell costs {2} less to cast if five or more cards are in your graveyard.

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.