msem-instigator

First strike
Disgraced 1 (This enters with a -1/-1 counter. Whenever it deals combat damage to a player, remove all -1/-1 counters from it.)

Tap up to two target creatures. Those creatures don't untap during their controller's next untap step.
Menagerie — If there are five or more creature types among creatures you control, scry 3.

Whenever Scathing Critics deals combat damage to a player or planeswalker, put a +1/+1 counter on it.

Target player reveals their hand. You choose a nonland card from it. That player discards that card. Create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)

Counter target spell. Tap all lands that spell's controller controls and that player loses all unspent mana.

Put target creature on top of its owner's library. All other creatures that player controls get -2/-2 until end of turn.

Exile target creature. Return that card to the battlefield under its owner's control at the beginning of the next end step.

{3}, {T}: Draw a card.
Crew 3 (Tap any number of creatures you control with total power 3 or greater: This Vehicle becomes an artifact creature until end of turn.)

Whenever another creature dies, you gain 1 life.

Flying
Whenever Scavenging Hilakites attacks, you may sacrifice another creature. When you do, Scavenging Hilakites deals damage equal to the sacrificed creature's power to any target.

Reach
When Scavenging Pack enters, you may destroy target artifact with mana value 2 or less.

As Scavenging Sandwurm enters, choose decay or remain.
When Scavenging Sandwurm dies,
• Decay — Draw a card.
• Remain — Create a 2/2 black Zombie creature token.

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.)

Choose one or both —
• Scene to Cinders deals 2 damage to each token creature.
• Scene to Cinders deals 2 damage to each nontoken creature.

Enchant creature or land
Whenever enchanted permanent becomes tapped for the first time each turn, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on that creature, then put the card back or put it into your graveyard.)

Scholar of the Staff can't block.
Inspired — Whenever Scholar of the Staff becomes untapped, up to one target creature can't block this turn.

Attacking creatures get -3/-0 until end of turn.

Search your library for an instant card or a card with flash, reveal it, put it into your hand, then shuffle.
Flashback {5}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Schoolmaster gets +1/+1 for each other Merfolk you control.
When Schoolmaster enters, create a 1/1 white Merfolk creature token.

Whenever one or more nontoken Merfolk you control attack, create a 2/1 red Merfolk creature token.

Scion of Belmord has lifelink as long as it's embattled. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Menace
When Scion of Calamities enters, exile the top two cards of your library. Until the end of your next turn, you may play one of those cards.
Whenever a Mountain you control enters, you may aetherize Scion of Calamities. (To aetherize, create a token that's a copy of it, then exile that token.)

When this creature enters, you may put a -1/-1 counter on a creature you control. If you do, look at the top five cards of your library. You may reveal a land card from among them and put it into your hand. Put the rest into your graveyard.

Indestructible
Whenever a creature an opponent controls dies, put five +1/+1 counters on Scion of Death.

Deathtouch
When Scion of Desolation enters, put target creature card with mana value 3 or less from a graveyard onto the battlefield under your control.
Whenever a Swamp you control enters, you may aetherize Scion of Desolation. (To aetherize, create a token that's a copy of it, then exile that token.)