msem-instigator

Whenever you cast a spell during an opponent's turn, creatures you control get +0/+1 until end of turn.

Tortle Traveler enters tapped.
When Tortle Traveler enters, 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 this creature, then put the card back or put it into your graveyard.)

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

Return target instant or sorcery card from your graveyard to your hand. Then if this spell wasn't foretold, discard a card.
Exile Spark of Inspiration.
Foretell {R} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Equipped creature has hexproof and improve {1}. ({1}: Put a +1/+1 counter on that creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
{4}: Put Faithforged Pauldron from your hand onto the battlefield attached to target creature.
Equip {1}

Whenever one or more creatures deal combat damage to you, put a -1/-1 counter on one of them.
Attain {5}{W} ({5}{W}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

Whenever one or more artifacts you control enter, put a +1/+1 counter on Octopus Shiny-Grabber and you gain 1 life.

Target player draws X cards and loses X life, where X is the number of enchantments you control.

When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.
Compose (Then if you cast this from your hand, exile it and create a Saga token with “r3—You may cast a copy of this card from exile without paying its mana cost.”)

{T}: Add {C}.
{1}, {T}, Sacrifice Perilous Passage: Destroy target nonbasic land. Activate only if an opponent controls four or more lands.

({T}: Add {U} or {B}.)
Flooded Morass enters tapped unless you control a basic Island or a basic Swamp.

When The Moon Rises enters, exile all opponent's graveyards.
At the beginning of your upkeep, each opponent loses 1 life.

{2}{B}{B}, Exile Reclusive Augur from your graveyard: Return another target creature card from your graveyard to the battlefield. Activate only during your turn.

Remove all -1/-1 counters from target creature. That creature gets +3/+3 and gains trample until end of turn.

Destroy target colorless nonbasic permanent. Harsh Erosion deals 2 damage to that permanent's controller.

{2}{R}: Target creature can't block this turn.

{T}, Sacrifice a land: Draw a card.
When Glutton of Zhava dies, return all land cards from your graveyard to the battlefield tapped.
Foreshadow {4}{G}{G} (You may cast this spell for its foreshadow cost. If you do, also trigger its “dies” abilities when it enters.)

Whenever Seasoned Lookout deals combat damage to a player, it voyages. (If it isn't blocking or targeted by another spell or ability, it phases out.)
Whenever Seasoned Lookout phases in, reveal the top card of your library. If it's a land card, put it onto the battlefield. Otherwise, put it into your hand.

Improve {R/W} ({R/W}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
Whenever an embattled creature you control attacks, you may exile the top card of your library. During any turn you attacked with an embattled creature, you may play that card. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

When Powercell Cultivator enters, create a tapped colorless Powercell artifact token with “{T}: Add {C}.”
Artifacts you control have “{T}: Add one mana of any color.”

As long as Armed Vendor is enchanted or equipped, it gets +1/+0 and has menace.

Wise Old Oak enters tapped unless you control a basic Forest.
{T}: Add {G}.
{3}{G}{G}: Until end of turn, Wise Old Oak becomes a 4/4 green Treefolk creature with “Whenever this creature deals combat damage to a player, draw a card.” It's still a land.

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.)
Whenever a player discards a card, draw a card from the archived library.

Menace
When Beatrice enters, target opponent reveals their hand. Exile a nonland card from it. During any turn that player lost life, you may cast that card and mana of any type can be spent to cast that spell.

Flying, lifelink
Morph {4}{B}
When Soul Cajoler is turned face up, manifest the bottom card of your library. (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.)