msem-instigator

When Briarform Apothecary enters, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
Sacrifice a token: Briarform Apothecary gets +2/+2 until end of turn.

Destroy target creature unless its controller pays {3}.

Satrapies you control have “{2}, {T}, Pay 1 life: Draw a card.”
Satrapycycling {2} ({2}, Discard this card: Search your library for a Satrapy card, reveal it, put it into your hand, then shuffle.)

Choose one —
• Counter target noncreature spell.
• Peer into the Cosmos deals 3 damage to target creature.
• Until end of turn, damage that would reduce your life total to less than 1 reduces it to 1 instead.
Monument {1}{U}{R}{W} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

Trample
Resolute — At the beginning of combat on your turn, if Helicos Gargantua's power is greater than its base power, double its power until end of turn.

Siphon (Each -1/-1 counter you put on your creatures up to their remaining toughness while casting this pays for {1}.)
Costly Ambush deals damage equal to the greatest power among creatures you control to target creature or planeswalker.

Give any number of permanents and/or players with counters on them another counter of each kind already there. Whenever you cast a spell this turn, repeat that process.

(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 Dawn Over Nizev enters, draw three cards.
When Dawn Over Nizev is defeated, exile it. If you do, you may cast a spell from your hand without paying its mana cost.

{T}: Add {C}.
{1}, {T}: Add {G}{U}.

Target creature gets +1/+1 for each creature you control and gains flying and vigilance until end of turn.

Wither (This deals damage to creatures in the form of -1/-1 counters.)

At the beginning of each player's upkeep, sacrifice Hayuan, the Misjudged if that player controls a creature with power 2 or less.
When Hayuan dies, create X Idol tokens, where X is the number of creatures you control. (They're artifacts with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)

{T}: Add {U} or {R}.
{U}{R}, {T}: Target creature gains flying until end of turn.

Heroic — Whenever you cast a spell that targets Mira and Kalisti of Akros, copy that spell. You may choose new targets for the copy. (The copy isn't cast. A copy of an Aura spell becomes a token.)

Whenever a nontoken creature you control dies, create a 1/1 black and green Citizen creature token and you gain 1 life.

At the beginning of your upkeep, if each opponent controls more lands than you, search your library for a basic land card, reveal it, and put it into your hand, then shuffle.

Vigilance
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Each player sacrifices two creatures, then gains 2 life and draws a card for each creature they sacrificed this way.

Enchant creature
Enchanted creature is a Horror with base power and toughness 3/3 and loses all other creature types and abilities.
Whenever enchanted creature deals combat damage to a creature, create a token that's a copy of Plagas Infestation and attach it to the damaged creature.

Each creature with a law counter on it can't attack or block.
{2}{W}, {T}: Remove all law counters from all permanents, then put a law counter on target creature.

Prowess
{3}{R}, Sacrifice Goblin Experimenter: Return target sorcery card from your graveyard to your hand.

Whenever you sacrifice a creature, you may pay {B}{G}. If you do, put a +1/+1 counter on Bloodblade Mercenary and draw a card.

Menace, haste
Whenever another player casts a spell that targets Plasma Addict, that player gains control of Plasma Addict.

When Occult Mastermind enters, create two 2/2 black Zombie creature tokens. When Occult Mastermind is no longer on the battlefield, sacrifice two Zombies.