msem-instigator

{T}: Add {C}.
{T}, Sacrifice a creature: Add one mana of any color.

If a creature entering under you control causes an ability to trigger, you may pay -1. Whenever you do, copy that ability. You may choose new targets for the copy.
[+1]: Exile target creature. Return that card to the battlefield tapped under its owner's control at the beginning of the next end step. If you don't control it, it enters with a stun counter.
[–2]: Draw a card and gain 2 life.

Target opponent reveals their hand. You choose a nonland card from it. That player discards that card.
Create a Function token with “Draw a card if a player discarded a card this turn.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Whenever you cast your second spell during each of your turns, you may activate one of Salome's loyalty abilities.
[+1]: Draw a card. Untap up to two lands.
[–4]: Destroy all creatures.
[–8]: You get an emblem with “You may pay {0} rather than pay the mana cost for the second spell you cast each turn.”

First strike
Whenever Ogura, Contracted Rebel attacks, you may create a token that's a copy of another attacking creature with power less than or equal to Ogura's. Sacrifice the token at the beginning of your next end step.
{R}: Ogura gets +1/+0 until end of turn.

Vigilance, menace, trample, haste
Whenever you cast a spell, you may consume. If you do, put a +1/+1 counter on Thunderous Avarice. (To consume, sacrifice another creature or exile a creature card from your graveyard.)
Whenever an opponent casts a spell, they may consume. If they don't, put a +1/+1 counter on Thunderous Avarice.

[0]: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
[–2]: Exile target creature. Create a battle token with three defense and “When this battle leaves the battlefield, return the exiled card to the battlefield under its owner's control.” You're protecting it.
[–5]: Create two 0/0 black Phyrexian Germ creature tokens, then put two +1/+1 counters on each creature you control.

Whenever a nontoken creature you control dies, create a 1/1 black Spirit creature token with flying.
[+1]: Each opponent loses 2 life and you gain 2 life.
[–2]: You may sacrifice a creature. When you do, destroy target nonland permanent.

Return up to two target creature cards with total mana value 3 or less from your graveyard to the battlefield tapped.
Cycling {2} ({2}, Discard this card: Draw a card.)

Whenever another creature you control enters, target opponent loses 1 life and you gain 1 life.
Sacrifice Somber River Bearer: Creatures you control gain indestructible until end of turn.

Prowess, prowess, prowess
Noncreature spells you cast cost {1} less to cast.

When Paul, Rock Bottom dies, you may discard a card. If you do, return this card from your graveyard to your hand at the beginning of the next end step.
[+1]: Draw a card, then discard a card.
[0]: Until end of turn, Paul becomes a 2/2 Construct creature with prowess. Prevent all damage that would be dealt to them this turn.
[–3]: Return target instant or sorcery card from your graveyard to your hand.

Menace
When this creature dies, create two tapped 3/2 colorless Eldrazi creature tokens. Put a stun counter on one of them.

Mill three cards. When you do, return another nonland card from your graveyard to your hand.

Whenever one or more creatures you control deal combat damage to an opponent, choose up to that many —
• Create a Weapon token and attach it to one of those creatures. (It's an Equipment with equip {2} and “Equipped creature gets +1/+1.”)
• Add {R}{W} at the beginning of your next main phase.
• Each player draws a card.

Choose one —
• Destroy target artifact or enchantment.
• Return target creature to its owner's hand.
• Draw a card.

[+2]: Until end of turn, Helene Trant becomes a 4/4 Human Warrior creature with hexproof and trample that's still a planeswalker. Prevent all damage that would be dealt to her this turn.
[–2]: Draw two cards.
[–4]: You get an emblem with “Whenever one or more creatures you control deal combat damage to a player, draw a card.”

Puzzlebox (Begin the game with this and another card you own from outside the game in the command zone, locked. That card is face down until you unlock this.)
{5}: Unlock Key to the Nexus. If {W}{U}{B}{R}{G} was spent to activate this ability, you may cast the revealed card without paying its mana cost. Otherwise, put that card on top of your library.

Flying
Spirited (When this creature enters, you may activate one of its activated abilities without paying its costs.)
{3}{U/B}{U/B}: Look at the top card of target opponent's library, then exile it face down. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any type to cast that spell.

Spirited (When this enters, you may activate one of its activated abilities without paying its cost.)
{1}, {T}, Discard a card: You gain 4 life.
{2}, {T}, Pay 2 life: Create a 1/1 colorless Construct artifact creature token. It can't block this turn.
{3}, {T}, Sacrifice a permanent: Draw a card.

{T}: Add {C}.
Sacrifice a nonland permanent: Ayala's Effigy becomes a 2/2 Construct artifact creature until end of turn.

Haste
Battle cry (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn.)
Whenever Goblin War Chariot becomes crewed, untap each creature that crewed it with mana value 1 or less. This ability triggers only once each turn.
Crew 3

When a creature you control scavenges Harvest Reaper, search your library for a colorless card, reveal it, put it into your hand, then shuffle.
Scavenge {4} ({4}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

When Masterwork Archivist enters, search your library and/or command zone for a legendary card, reveal it, then put it into your hand or graveyard. If you searched your library this way, shuffle.
When Masterwork Archivist dies, you may draw a card.

[+1]: Add {C}. Spend this mana only to cast artifact or colorless spells.
[0 ]: Create a 1/1 colorless Construct artifact creature token.
[–2]: Look at the top six cards of your library. You may reveal an artifact or colorless card from among them and put it into your hand. Put the rest on the bottom in a random order.