msem-instigator

Target player sacrifices an attacking or blocking creature.

When Ill-Fated Seer enters, each player sacrifices a creature. If they can't, Ill-Fated Seer deals 3 damage to them.
Revive {2}{B}{R} ({2}{B}{R}, Exile this card from your graveyard: Create a token that's a copy of this card, except it has no mana cost. Activate only as a sorcery.)

Whenever Illumination Savant attacks, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Put a +1/+1 counter on each artifact creature and enchantment creature you control.

Flash
Trample

You may have Imaginative Dreamer enter as a copy of any creature on the battlefield. When it does, it stops being a copy.

At the beginning of each opponent's end step, that player gets a poison counter unless damage was dealt this turn.

Enchant creature
Enchanted creature gets +2/+2 and has trample and indestructible.

Whenever a face-down creature you control attacks, defending player loses 1 life.
{2}, Discard a card: Manifest the bottom card of your library. Activate only once each turn. (To manifest a card, put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Enchant creature
Enchanted creature can block any number of creatures each combat.

Escalate {G} (Pay this cost for each mode chosen beyond the first.)
Choose one or both —
• Target creature you control gains deathtouch and indestructible until end of turn.
• Target creature you control fights target creature you don't control.

Gestalt (When this or another creature enters under your control, you may merge it with the one in play, keeping counters and attachments. They become the permanent on top plus all abilities from under it.)
Whenever this creature attacks, target creature blocks it this combat if able.

Destroy target tapped creature. You gain 2 life.

Haste
When Inciting Bard enters, other creatures you control get +1/+0 and gain haste until end of turn.

Target creature gets -1/-1 until end of turn.
Threshold — You may destroy that creature instead if seven or more cards are in your graveyard.

When Inexperienced Martyr dies, each opponent loses 1 life.

Lifelink
Whenever Infectious Ego enters or attacks, exile the top card of target opponent's library. If it's a land card, that player gets a poison counter. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast that spell.

Once each turn, when a player casts a spell, you may choose two target players. Each of those players exiles cards from the top of their library until they exile a nonland card with mana value less than that spell's. They may cast those cards without paying their mana cost. Then they put the rest of the exiled cards on the bottom of their library in a random order. (The active player puts their spell on the stack first.)

When Influential Wildborn enters, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Whenever Inkwell Daggers enters or attacks, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

Enchant creature
Enchanted creature gets +2/+0 and has trample.

Inscrutable Realms enters tapped unless you control two or more other lands.
{T}: Add {W}.
{T}, Pay 1 life: Add {G} or {U}.

At the beginning of your upkeep, put a lore counter on Inspirational Copse, discard your hand, then draw a card for each lore counter on Inspirational Copse.

Escalate {R} (Pay this cost for each mode chosen beyond the first.)
Choose one or both —
• Untap all creatures you control.
• Take an extra turn after this one. Skip the untap step of that turn. Exile Inspire Actuality.