msem-instigator

[+1]: Add {W}{U}{B}{R}{G}.
[–1]: Exile the top three cards of your library. Until end of turn, you may play cards exiled with this permanent.
[–3]: Create a 5/5 Archon creature token that's all colors and has flying and “When this creature enters, it deals 5 damage to any target.”

Sacrifice a permanent, then draw cards equal to its mana value.
You may put a permanent card from your hand onto the battlefield if its mana value is less than or equal to the number of cards in your hand.

({T}: Add {G} or {W}.)
Heart of the Glade enters tapped unless you control a basic Forest or a basic Plains.

Surveil 2, then create a tapped X/X green Mutant creature token, where X is the number of card types among cards in your graveyard.

Vigilance
When Scion of Storms enters, create a 2/2 white Elemental creature token with flying.
Whenever a Plains you control enters, you may aetherize Scion of Storms. (To aetherize, create a token that's a copy of it, then exile that token.)

Whenever Organ Scavenger perseveres, each opponent loses 2 life. (A creature perseveres when it survives damage.)

Whenever Dodgy Infant becomes the target of a spell, you may change the target to another creature you control.

(As an Encounter enters, choose an opponent to protect it. You and others can attack it. When defense counters are removed, create a 0/0 Army token if you don't control one, then put that many +1/+1 counters on a Army you control.)
When Dawn Over Kaneh enters, return any number of creature cards from your graveyard with total mana value X or less to the battlefield. They become Armies in addition to their other types.

Haste
When Magma Crawler enters, creatures you control with flash or haste get +1/+1 until end of turn.

[+1]: Scry 1, then draw a card. You lose 1 life.
[–2]: Target player sacrifices a creature, then loses life equal to the greatest power among creatures they control.
[–5]: Choose a nonland card name. Exile all creatures and planeswalkers with that name, then search target player's graveyard, hand, and library for any number of cards with that name and exile them. That player shuffles.

{T}: Add {C}.
{2}, {T}, Sacrifice Lotus Barrens: Destroy target nonbasic land an opponent controls. You and that land's controller each create a colorless land token named Lotus Spring with “{T}: Add one mana of any color.”

Flying, haste
Whenever you attack with three or more creatures, harmonize three times. (To harmonize, trigger up to one harmony of a permanent you control.)
If you would harmonize, you may instead return Herald of Festivities from your graveyard to your hand.

Menace
At the beginning of your upkeep, put a prize counter on target permanent you don't control.
Whenever a permanent with a prize counter on it is put into a graveyard from the battlefield, return it to the battlefield under your control.

Motivate 1 (When this creature enters, you may motivate target creature with less power than this by putting a +1/+1 counter on it.)
When Merthilios' Escort motivates a creature, that creature gains first strike until end of turn.

Reach
Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Other Elementals you control get +1/+1 as long as Miroran Skycatcher has a +1/+1 counter on it.

When Ninhasir's March enters, it deals 3 damage to any target.
{1}{R}{R}: Transform Ninhasir's March. Activate only if your fealty to Mountains is five or greater.

Enchant opponent
Enchanted player plays with the top card of their library revealed.
Whenever enchanted player casts a spell, you may have them mill a card.

When Brawlhost Escapee dies, create a Function token with “Target creature you control fights target creature you don't control.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

When Diseased Prophet enters, each opponent loses 1 life.
Revive {B} ({B}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Flash
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.)

Flash
When Hexfang Ascetic enters, return target spell to its owner's hand.

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.

Whenever you activate a loyalty ability of a planeswalker, you gain 1 life.

Audition for green, then audition for green. (Create a 1/1 Construct Actor creature token, a Scout Role giving 2/3 and vigilance, or a Warrior Role giving 3/2 and trample. Roles replace older ones.)

Concord — Temple Attendant gets +1/+1 and has indestructible as long as there are four or more card types among permanents you control.