msem-instigator

({T}: Add {G} or {U}.)
Rainforest Spring enters tapped.

Create two 1/1 white Soldier creature tokens.

Sacrifice a creature: Rapacious Demon gets +1/+1 and gains flying until end of turn. Activate only as a sorcery.

When Realmwalker Domovoi enters, exile another target permanent you control. Return it to the battlefield under your control at the beginning of the next end step.

Haste
Whenever Reckless Pyremage becomes tapped, it deals 1 damage to each creature and each player.

When Relearn History enters, draw two cards.
You have no maximum hand size.

Return target creature card from your graveyard to your hand. Add {G}{G}{G}. Spend this mana only to cast creature spells.

Destroy target artifact, enchantment, or creature with flying.

Puzzlebox (Begin the game with this and another card you own from outside the game in the command zone, locked. That card is face down until you unlock this.)
{1}: If you control ten or more nonland permanents, unlock Riddle of Entropy.
As long as the revealed card is a permanent card, each nonland permanent you own is a copy of it.

At the beginning of your upkeep, you lose 1 life, then investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
Whenever you sacrifice a permanent, each opponent loses 1 life.

As long as your deck contains only blue and colorless cards, your minimum deck size is reduced by eight.

({T}: Add {U} or {R}.)
Roaring Cascade enters tapped.

Whenever Rolling Homestead becomes a creature, nourish 1. (To nourish 1, either put a +1/+1 counter on this creature or create a 1/1 white Citizen creature token.)
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

At the beginning of each upkeep, choose another permanent with the greatest mana value among permanents. Its controller sacrifices it.

At the beginning of your upkeep, you may put a card from your graveyard on the bottom of your library. If you do, you gain 2 life.
{2}, Sacrifice Rune of Rejuvenation: Draw a card.

Whenever a creature or planeswalker enters under an opponent's control, sacrifice Rune-Scribe's Trap unless you pay {R}. If you sacrifice it, it deals 6 damage to that permanent.

When Runebreaker Mage enters, return another target nonland permanent you control and target nonland permanent you don't control to their owner's hands.

When Sandbluff Enforcers enters, detain target creature an opponent controls. (Until your next turn, that creature can't attack or block and its activated abilities can't be activated.)

Creature spells you cast cost {2} less to cast.
Whenever a creature you control enters, if it doesn't have vanishing, put four time counters on it and it gains vanishing.

Each instant and sorcery card in your graveyard has reprise. The reprise cost is equal to its mana cost. (As you cast an instant or sorcery spell, you may exile one card with reprise from your graveyard and pay its reprise cost. If you do, add its effects to that spell.)
Reprising spells you control can't be countered.

Draw three cards, then manifest a card from your hand. (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.)

Flash
When Scholar of Reflections enters, you may switch target creature's power and toughness until end of turn.

Flying
Whenever an artifact you control enters, you may activate one of its activated abilities without paying its cost.

Create three 0/1 green Plant creature tokens.

Target creature gets +1/+1 and gains first strike until end of turn.
Fabled {3}{W} (Then if you cast this for its fabled cost, put it onto the battlefield transformed attached to that creature.)