msem-instigator

Whenever a creature you control enters, if you didn't cast it from your hand, put a +1/+1 counter on it.
{3}{W}: Exile target creature you control, then return it to the battlefield under its owner's control.

Gain control of target nonland permanent. The player that controlled it creates a 3/3 blue Squid creature token.

Whenever equipped creature deals combat damage to a player, put two balance counters on Staff of Equilibrium.
Remove a balance counter from Staff of Equilibrium: Staff of Equilibrium deals 1 damage to any target.
Equip {1}

Equipped creature gets +1/+1.
At the beginning of combat on your turn, choose flying, first strike, vigilance, trample, or haste. Equipped creature gains that ability until end of turn.
Equip {2}

Lifelink
When Stalked Healer enters, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Return target spell to its owner's hand. Its controller can't cast spells this turn. (Spells cast before this resolves are unaffected.)

({T}: Add {G}, {W}, or {U}.)
Stalwart Dominion enters tapped.

You gain 7 life.
Coalesce {5}{G}{G} (You may cast this from your graveyard for {5}{G}{G}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Flying
Starbane Elemental's power and toughness are each equal to the number of creatures with flying you control.
When Starbane Elemental enters, destroy all creatures without flying.

Trample, ward {1}
Whenever Stardust Surveyor deals combat damage to a player, you may mill cards until you mill a creature card. When you do, return target creature card from your graveyard to your hand.

Shimmer (Whenever this creature attacks, create a tapped and attacking token that's a copy of it. Exile the token at the beginning of the end step.)
Each other creature you control gets +1/+1 for each creature you control with the same name as it. (A token's name is its creature types unless specified.)

Whenever you draw a card, put a dream counter on Stargazing.
Remove seven dream counters from Stargazing and exile it: Shuffle your hand and graveyard into your library, then draw seven cards.

Reveal the top five cards of your library. An opponent separates those cards into two piles. Put one pile into your hand. You may cast a nonland card with mana value 3 or less from the other pile without paying its mana cost, then put that pile into your graveyard.

{T}: Add {C}.
{3}, {T}: Aetherize target permanent you control. Activate only as a sorcery. (To aetherize, create a token that's a copy of it, then exile that token.)

{T}: Add {C}.
{2}, Pay 2 life: Starved Oasis becomes a 4/2 Elemental creature until end of turn. It's still a land.

Until end of turn, if a source you don't control would deal damage to you or cause you to lose life, mill that many cards instead.

Target opponent discards a card at random. If that card's mana value is 3 or less, you may cast it without paying its mana cost.

Enchant creature
When Sticky Fingers enters, draw a card.
Enchanted creature gets +2/+0 and can't be blocked.

Counter target noncreature spell. Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

When Still-Smoke Skirmisher dies, each opponent loses 1 life and you gain 1 life. Then return Still-Smoke Skirmisher to the battlefield at the beginning of the next end step if it was sacrificed.

Creature cards in your graveyard have revive. The revive cost is equal to their mana cost. (Pay that creature's mana cost, Exile that card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

When Stillmarsh Brinecatcher enters, return another target nonland permanent to its owner's hand.
At the beginning of your end step, if you control a permanent with mana value 5 or greater, you may sacrifice Stillmarsh Brinecatcher. If you do, draw a card and create a 3/2 colorless Horror creature token.

Stinging Swordfish has first strike as long as it's attacking.
When Stinging Swordfish dies, create an Equipment enchantment artifact token named Fish Sword with “Equipped creature gets +3/+1,” “Equipped creature has first strike as long as it's attacking,” and equip {2}. You may attach that token to a creature you control.

When Stoic Observation enters, mill two cards, then you may return a creature card from your graveyard to your hand.
{3}{G}, Exile a creature card from your graveyard: Create a 2/2 green Wolf creature token. You gain 2 life.

Choose a nonland card type. Target player reveals their hand. You choose a card of the chosen type from it. That player discards that card.