msem-instigator

Menace
When Spaceship Invader enters, destroy target creature you don't control with mana value 3 or less.

Whenever you activate one of Ai's loyalty abilities, create a 2/2 colorless Soldier artifact creature token with that ability, except it costs +1 to activate.
[+1]: Ai deals 1 damage to target player or planeswalker. You gain 1 life.
[–3]: Draw a card. You lose 1 life.
[–7]: Each opponent sacrifices a permanent and discards a card.

Flying, trample
Whenever an opponent casts a noncreature spell, that player loses 5 life unless they sacrifice a creature or discard a card.

Menace (This creature can't be blocked except by two or more creatures.)
When Spawn of Shadows enters, each player loses 4 life.

Manifest all cards from all players' hands. (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.)

Menace
Whenever you cast a cryptic spell, you may return target creature card from your graveyard to your hand. (Artifacts, enchantments and modal spells are cryptic.)

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
Target creature gets -2/-2 until end of turn. If you're in a renaissance, it gets -5/-5 until end of turn instead.

When Specimen Collector enters, you may salvage a creature card. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

Rouse 4. Sacrifice a creature at the beginning of the next end step. (Distribute four +1/+1 counters among permanents you control. If they aren't creatures, tap them and they become 0/0 creatures in addition to their other types.)

Flying
When Spectre of Terror deals combat damage to a player, that player discards a card.
Madness {1}{B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

As an additional cost to cast this spell, exile X cards from your graveyard.
Choose one —
• Target player mills X cards.
• Look at the top X cards of your library. Put one into your hand, and the rest on the bottom of your library in any order.

Whenever you cast a noncreature spell, you may pay {U}. If you do or the spell was cast from your graveyard, draw a card.

If an ability of a creature or planeswalker an opponent controls was activated this turn, you may pay {1}{B} rather than pay Spike Wall Trap's mana cost.
Destroy target creature or planeswalker.

When Spiked Burrower dies, if it didn't have a counter on it, return it to the battlefield under your control with a +1/+1 counter or a lifelink counter on it.

At the beginning of each player's upkeep, that player discards a card. If that player has no cards in hand, instead they sacrifice a permanent. If they control no permanents, instead they lose the game.

Whenever Spirit of Infamy attacks, 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.)
Spirit of Infamy gets +2/+0 for each bounty counter on it.

Flying, deathtouch
Creatures that aren't Spirits or Warlocks get -1/-1.

Flying, lifelink
Skip your draw step.
Pay 3 life: Draw three cards. Activate only as a sorcery and only once each turn.

Target creature gets -1/-1 until end of turn. (Cast a copy of this spell once while this creature is on the battlefield.)

Enspirit (As you cast this spell, you may exile a nonenchantment creature you control until this leaves the battlefield or fails to resolve. Reduce this spell's cost by the exiled card's mana value.)
Menace

Target creature gets +2/+2 and gains lifelink until end of turn. Whenever that creature perseveres this turn, target opponent loses 2 life. (A creature perseveres when it survives damage.)

Once during each of your turns, when you sacrifice a creature, enchantment, or planeswalker, you may choose one —
• Search your library for a card that shares a card type with the sacrificed permanent, reveal it, put it into your hand, then shuffle.
• Target opponent sacrifices a permanent that shares a card type with the sacrificed permanent.

Lifelink
Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
Whenever Spoiled Oracle mentors a creature, that creature gains lifelink until end of turn.

At the beginning of your upkeep, each opponent mills two cards.
{3}{B}: Exile target nonland card from an opponent's graveyard. Copy it. You may cast the copy. Activate only as a sorcery. (You still pay its costs, including color. Copies of permanents enter as tokens.)

Whenever Sporecaster or another Insect you control enters, each opponent loses 1 life.