msem-instigator

Target creature gains double strike until end of turn. Mill a card.

As Enlightened Sigil enters, choose a card type.
Spells you cast of the chosen type cost {1} less to cast.

Vigilance
Whenever one or more cards leave your graveyard, surveil 1.

Tinyvale Treetops enters tapped unless you played it from exile.
{T}: Add {G} or {W}.

Rhapsody {4}{R}{R} (Pay {4}{R}{R} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Double strike

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Loot Hoarder Dragon enters, gain control of target artifact.

{2}, Sacrifice Bottled Fate: Put the top card and bottom card of your library into your hand.

Return target creature to its owner's hand. Scry 1.

Enchant creature
Enchanted creature gets +0/+2 and can block an additional creature each combat.

When Limbhacker Blade enters, each opponent discards a card.
Equipped creature gets +2/+0.
Equip {2}

Motivate 2 (When this creature enters, you may motivate target creature with less power than this by putting two +1/+1 counters on it.)

Whenever a creature you control enters, you may have target creature get +1/+1 and gain flying until end of turn.

Target creature gets -2/-2 until end of turn. When that creature dies this turn, create a tapped 2/2 black Zombie creature token.

Flying, ward {3}
Whenever Sphinx of Myriad Futures attacks, look at the top three cards of your library and reveal one of them. The defending player may have you put the revealed card into your hand. If they don't, put the other two cards into your hand. Then put the remaining cards into your graveyard.

Harness (You may tap a creature you control as you cast this spell. If you do, reduce this spell's mana cost by that creature's power.)
Put two +1/+1 counters on target creature. If this spell was harnessed, also put a +1/+1 counter on the creature that harnessed it.

Legendary spells you cast have nonlegendary cascade. (When you cast that spell, exile cards from the top of your library until you exile a nonlegendary nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Enchant creature
Enchanted creature gets +3/+3 and has flying and vigilance.
Lifecycle {3} ({3}, Discard this card: Create two tapped 1/1 colorless Elemental creature tokens.)

{W}, {T}: Tap target creature.

Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{3}{G}: Mill three cards. Target creature gets +X/+X and gains trample until end of turn, where X is the number of land cards in your graveyard.

Target creature gets -2/-2 until end of turn. Mill two cards.

Double strike

When Blessed Bladewright enters, create a Weapon token. (It's an Equipment artifact with “Equipped creature gets +1/+1” and equip {2}.)
Whenever an Equipment token you control enters, attach it to up to one target creature you control.

Flash
If an opponent would draw a card, that player exiles the top card of their library instead. During each player's turn, that player may play that card for as long as it remains exiled.

Archive 4 (As this enters, shuffle the top four cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
At the beginning of each opponent's upkeep, that player may pay 2 life. If they do, you gain 2 life. Otherwise, you draw a card from the archived library.