msem-instigator

{T}: Add {C}.
{3}, {T}: Create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Overcast — Whenever you cast a spell, create a 1/1 black Bird creature token with flying and menace if {C} was spent to cast it.
Whenever three or more creatures you control deal combat damage to a player, return target card from your graveyard to your hand.

Menace (This creature can't be blocked except by two or more creatures.)
Infiltrate (Whenever one or more attacking creatures you control aren't blocked, this creature gets +1/+1 until end of turn.)

Target opponent reveals their hand. You choose a nonland card from it. That player exiles that card.
Each player conjures a card named Data-Point into their hand. (It's a sorcery that costs {2} with “Draw a card.”)

(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 A Matricide Most Foul enters or is defeated, each opponent exiles a permanent they control with the highest mana value among nonland permanents they control.

Equipped creature gets +2/+0 and has first strike.
Equip Cleric or Knight {1}
Equip {3}

Enchant creature
When Melt the Chains enters, exile the top two cards of your library. Until the end of your next turn, you may play those cards.
Enchanted creature gets +3/+0.

Exile any number of target creatures. For each creature exiled this way, its controller creates a 3/2 green Crocodile creature token with trample.

Whenever another creature you control enters, Sunblessed Orator deals 1 damage to each opponent and you gain 1 life.

Flying, trample, haste
Whenever you activate an ability of a nonland permanent, you may have Ilieth, Transcendent deal 2 damage to target creature.
{2}{R}: Creatures you control get +2/+0 until end of turn.

Enchant creature
Enchanted creature can't attack, block, or be sacrificed.

Whenever you create one or more creature tokens, you may pay {1}{G/W}. If you do, put a +1/+1 counter on Sylshal, Life's Gyre and on each creature token you control.

Whenever you make first contact, exile the top card of your library. You gain life equal to its mana value. You may play that card until the end of your next turn. (You make first contact the first time each turn you cast a spell with a name not in your graveyard or control already.)

Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn.

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

Trample
Whenever Horrific Progenitor deals damage to a player, for each damage dealt, that player loses 3 life unless they sacrifice a nonland permanent or discard a card.

Archive 5 (As this enters, shuffle the top five cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Recursive — Xirix's Study has all nonrecursive abilities of all Study cards in graveyards except for their archive abilities.

As Rhythm of Kaneh enters, choose Andazir or Mahara.
• Andazir — Whenever a creature you control attacks, defending player discards a card.
• Mahara — Whenever a nontoken creature you control dies, amass Soldiers X, where X is that creature's power.

{2}{B/G}: Return Silthway Scuttler from your graveyard to your hand.
{2}{B/G}, Exile Silthway Scuttler from your graveyard: Put two +1/+1 counters on target creature.

Choose two or four —
• Search your library for a Forest card, reveal it, put it into your hand, then shuffle.
• You may put a land card from your hand onto the battlefield tapped.
• You gain 4 life.
• Conjure a card named Fatigue and put it on top of your library. (It's a colorless sorcery that costs {2} with “Draw a card.”)

Reach
When Automated Overwatch enters, create a Function token with “If this spell would create one or more tokens, it creates twice that many of those tokens instead.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Destroy all creatures, then return all nonland permanents to their owner's hands.

Each opponent sacrifices a creature or planeswalker. If you own a foretold card in exile, you gain 4 life.

Flying
Whenever you cast an instant or sorcery spell, Scourge of the Sun gets +1/+0 until end of turn. If you spent four or more mana to cast that spell, Scourge of the Sun gets an additional +1/+0 until end of turn.