msem-instigator

This spell costs {X} less to cast, where X is the greatest power among creatures you control.
{1}: Target creature in Indomitable Anchorite's pack gains indestructible until end of turn. (Two or more creatures you control with equal power are in a pack.)

Creatures you control attacking causes their death knell to trigger.
Death knell — Indomitable Spirit gets +2/+2 and gains trample until end of turn. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)

Flash
Enchant creature
When Ineffable Patronage enters, it deals 4 damage to up to one target attacking or blocking creature.
Enchanted creature gets +2/+2.

This spell can't be countered.
Inescapable Blaze deals 6 damage to any target.

Enchant opponent
Creatures enchanted player controls get -2/-2.
Whenever enchanted player casts a noncreature spell, they lose 2 life and you gain 2 life.

When Infamous Bilgecaptain enters, forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.)
Other Pirates you control get +1/+1.
At the beginning of your end step, you may put a Pirate card with mana value less than or equal to the number of artifacts you control from your hand onto the battlefield.

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.

At the beginning of your end step, shuffle your hand and graveyard into your library, then draw seven cards.

Hexproof
Whenever another creature you control becomes the target of a spell an opponent controls, you may submerge that creature. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)
{1}{U}{U}: Turn target face-down creature you control face up.

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
[+1]: Scry 1. If you're in a renaissance, draw a card.
[–2]: Return target nonland permanent to its owner's hand if its mana value is 3 or less or if you're in a renaissance.
[–6]: Create two 8/8 blue Kraken creature tokens. If you're in a renaissance, take an extra turn after this one.

[+1]: Look at the top two cards of your library. Put one of them into your hand and the other into your graveyard.
[–2]: Return target card from your graveyard to the battlefield face down.
[–6]: Turn any number of face-up nonland permanents of your choice face down.

You may pay {2}{U}{U} and tap an untapped Wizard you control rather than pay this spell's mana cost.
Choose up to one target creature on the battlefield and up to one target instant or sorcery card in your graveyard. Return those cards to their owner's hands, then exile Ingenious Solution.

Gain control of target creature if its power is less than or equal to the number of counters on creatures you control.

When Inner-Eye Obscurist enters, return each other creature that isn't in Inner-Eye Obscurist's pack to their owners' hand. (Two or more creatures you control with equal power are in a pack.)

[+1]: Each opponent puts a -1/-1 counter on a creature they control.
[–1]: Exile target card in a graveyard. You gain life equal to its mana value.
[–6]: Choose a number. You draw that many cards and you lose that much life.

Whenever Insatiable Abomination or another Horror you control enters, each player mills four cards.
Exile a creature card from your graveyard: Tap target Horror you control. It gains indestructible until end of turn.

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.

Creatures you control get +2/+1 until end of turn.

Harmony — Target creature gets +2/+2 until end of turn.
When Inspiring Band enters, harmonize. (Trigger up to one harmony of one permanent you control.)

Enchant creature
Whenever enchanted creature attacks, other creatures you control get +1/+2 until end of turn.

Scry 3, then reveal the top card of your library. Discard your hand, then draw cards equal to that card's mana value.

Creatures you control get +1/+1 until end of turn. Token creatures you control get an additional +1/+1 until end of turn.

Until end of turn, gain control of target creature and it gains haste. Untap it.
Fuse (You may cast one or both halves of this card from your hand.)

Whenever a creature enters, it deals damage equal to its power to any target of its controller's choice.
When Interplanar Raid enters, you may aetherize target creature you control. (To aetherize, create a token that's a copy of it, then exile that token.)