msem-instigator

Motivate 1 (When this creature enters, you may motivate target creature with less power than this by putting a +1/+1 counter on it.)

Haste
When Jetskate enters, if you've drawn two or more cards this turn, it deals 2 damage to any target.
Cycling {R} ({R}, Discard this card: Draw a card.)

({T}: Add {U}.)
Moon of the Frozen Dusk enters tapped.
{1}{U}, {T}: Scry 1.

Reach, deathtouch

Equipped creature gets +2/+0 and can't be blocked.
Whenever a Rogue you control attacks, you may pay {1}. If you do, attach Saber of Defiled Rites to it.
Equip {5}

Whenever you cast a cryptic spell, Oasis Cattle gets +1/+1 until end of turn, then untap it. (Artifacts, enchantments, and modal spells are cryptic.)

Flying
Other creatures you control with flying get +1/+0.

Counter target spell unless its controller pays {2}.
Put a +1/+1 counter on a creature you control.

Vigilance, reach
When Winter Widow enters, you may destroy target creature with flying.

Flying
When Pyre Apostle enters, discard your hand, then draw three cards.
Madness {3}{R} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Reach
Lupine Skygrazer enters with a +1/+1 counter on it if three or more colors of mana were spent to cast it.

First strike, haste
Whenever Kragnoss' Battlecharger attacks, it gets +1/+0 until end of turn for each attacking creature.

{T}: Draw a card, then discard a card.
Sacrifice Ghislain, Cryptbreaker: You may cast target creature, instant or sorcery card from your graveyard this turn. If that spell would be put into your graveyard, exile it instead. Activate only during your turn.

Whenever Tortle Veteran or another Turtle you control enters, that creature 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.)

Enchant player
If enchanted player would shuffle their library, instead that player chooses a permanent they control and a card from their hand, shuffles them into their owner's libraries, then loses 3 life.

When Old-Oath Conviction enters or leaves the battlefield, create a 1/1 white Cleric creature token with lifelink.
{3}{B}, Sacrifice Old-Oath Conviction: Draw a card. Activate only as a sorcery.

Whenever Fox of the River Run attacks, if you control a creature with power 4 or greater, you may discard a card. If you do, draw a card.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Nimble Elemental deals combat damage to a player, you may draw a card. If you do, discard a card.

Trample, haste
When Oil Driller enters, salvage two cards at random. (Exile those cards from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)
At the beginning of your end step, sacrifice Oil Driller.

When Veins of the Intisuyu enters, draw a card, then choose a card name.
Whenever you cast a spell with the chosen name, search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

If this spell was foretold, target player creates a 4/4 red Dragon creature token with flying. Apex's Prey deals damage equal to the greatest power among creatures you control to up to one target creature or planeswalker.
Foretell {1}{R}{R}{G} (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.)

Flash
Flying

Enchant creature
Enchanted creature gets +2/+2 and can't be blocked as long as defending player controls a Desert.

Enchant player
Whenever one or more creatures attack enchanted player, their controller may sacrifice a creature. If they do, enchanted player loses 3 life, sacrifices a nonland permanent, and discards a card.

Poisonous 3 (Whenever this creature deals combat damage to a player, that player gets three poison counters.)
When Sankataar Assailant enters, choose a counter on target permanent or player. Give that permanent or player another counter of that kind.