msem-instigator

Return up to one target artifact card from your graveyard to your hand.
Put the bottom card of your library into your hand.

When Repurposed Custodian enters, shuffle any number of target cards from graveyards into their owner's libraries.

Whenever you sacrifice a permanent, you may put a soul counter on Soul's Guidestone.
As long as there are five or more soul counters on Soul's Guidestone, it's a 6/6 Golem artifact creature with menace and vigilance.

{T}, Sacrifice Ruined Citadel: Search your library for a Mountain or Plains card and put it onto the battlefield tapped, then shuffle.

Flying, prowess
When Chronosphere Sovereign enters, nonbasic permanents target opponent controls don't untap during their controller's next untap step.
When Chronosphere Sovereign dies, it deals 3 damage to each tapped creature you don't control. Destroy each tapped artifact you don't control.

Whenever Watchkeeper Deserter attacks, discard up to two cards, then draw that many cards. Watchkeeper Deserter gets +X/+0 until end of turn, where X is the total mana value of the discarded cards.

You mill two cards, draw two cards, lose 2 life, and create two Treasure tokens. (They're artifacts with “{T}: Sacrifice this permanent: Add one mana of any color.”)

When Matron of Machines dies, put a +1/+1 counter on up to one target creature.
{3}{W}, Exile Matron of Machines from your graveyard: Create two 1/1 colorless Construct artifact creature tokens. Activate only as a sorcery.

When Backstage Broken enters, create a 1/1 colorless Construct Actor creature token.
Whenever a token you control leaves the battlefield, you gain 1 life.

Enchant creature or planeswalker
You control enchanted permanent.
Permanents you control but don't own have hexproof.

Choose one or both —
• Put target detained creature on top of its owner's library.
• Detain target creature. (Until your next turn, that creature can't attack or block and its activated abilities can't be activated.)

(As an Encounter enters, choose an opponent to protect it. You and others can attack it. When defense counters are removed, create a 0/0 Army token if you don't control one, then put that many +1/+1 counters on a Army you control.)
When Danaj Rising enters, target player reveals their hand. You choose a nonland card from it. That player discards that card. You lose 1 life.

Target creature gains winnow until end of turn if you attacked this turn. Searing Insult deals 2 damage to that creature. (Damage dealt to it also causes its controller to lose that much life.)

{2}{R/G}: Wildershrine Warden gets +2/+2 until end of turn. You may have it assign its combat damage this turn as though it weren't blocked. Activate only once each turn.

Whenever a creature you control deals combat damage to a player, it cackles. (Put a menace counter on it. If it already has menace, it deals 1 damage to each opponent instead.)
{3}{B}: Each creature you control with menace gains lifelink until end of turn.

Target opponent reveals their hand. You choose a nonland card from it and exile that card.
Recruit. (Create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)

Menace
Whenever you cast a spell from anywhere other than your hand, each opponent discards a card if it's your turn. Otherwise, each opponent loses 2 life.

As an additional cost to cast this spell, sacrifice a creature or pay {3}.
Destroy target creature with power 3 or less.

If a source you control would deal noncombat damage, it deals double that damage instead.

Flying
Whenever you gain life, target creature an opponent controls gets -1/-1 until end of turn.

{B}, Discard a card: Post a bounty on target creature. (Put a bounty counter on that creature. It has “When this creature dies, each opponent draws a card” as long as it has a bounty counter on it.)

Haste
LH-6 Brutality can't attack or block unless you have two or fewer cards in hand.
{T}: Each player discards a card. Activate only as a sorcery.

{T}: Untap another target nonland permanent. Activate only as a sorcery.

Vanishing 3 (This permanent enters with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
Remove a time counter from Dwindling Stores: Add one mana of any color.

Hexproof
Spells you cast cost {1} less to cast for each creature you control that shares a creature type with that spell.