msem-instigator

Haste
Storm Entity enters with a +1/+1 counter on it for each other spell cast this turn.

Until end of turn, creatures target player controls lose all abilities and have base power and toughness 0/2.
Inscribe {4}{B}{B} ({4}{B}{B}: Exile this card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)

Stormbred Elemental gets +1/+1 as long as you control an Island.
{U}: Stormbred Elemental gains flying until end of turn.

{T}: Add {C}.
{T}, Exile two cards from your graveyard: Add {U} or {R}.

Stormcharged Pyre enters tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Flying
Prophecy {0} (Once each turn, you may exile a card with prophecy as you reveal it. When you do, you may cast it for its prophecy cost as long as it's exiled.)

Strange Harbor enters tapped unless you have 15 or less life.
{T}: Add {U} or {R}.

Target creature gets -3/-3 until end of turn.

Target creature gets +2/+2 until end of turn. Untap it.

Each player chooses one card in their hand, then discards the rest.

Target player gains X life.

Return target creature to its owner's hand.
Draw a card.

When Street Performer enters, create a 2/1 blue Illusion creature token with “When this creature becomes the target of a spell or ability, sacrifice it.”

Scry 3, then reveal the top card of your library. Target creature gains trample and gets +X/+X until end of turn, where X is that card's mana value.

Enchant creature
When Strength in Imagining enters, if it enchants a face-down creature, put a +1/+1 counter on that creature.
Enchanted creature has flying and trample.

Enchant creature
Enchanted creature gets +1/+2.

Counter three target spells.

Target creature gets +2/+0 and gains flying and first strike until end of turn.

Bulwark — {2}{G}: Stronghold Recruit gets +2/+2 until end of turn. Activate only once each turn and only if you control a creature with toughness 4 or greater.

When Student of Secrets enters, fateseal 1. (Look at the top one cards of an opponent's library, then put any number on the bottom and the rest on top in any order.)

Prowess
Art of war — At the beginning of your end step, if Student of Shigure dealt damage to an opponent this turn, you may draw a card, then discard a card.

When Student of the Crane enters, create a 1/1 white Bird creature token with flying.

Search your library for up to two creature cards and reveal them, then shuffle. Put one on the bottom of your library and the rest on top.

Return target nonland permanent to its owner's hand. If you control an artifact, draw a card.

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Whenever a creature you control becomes renowned, you may have it fight target creature you don't control. (Each deals damage equal to its power to the other.)