msem-instigator

Whenever you make first contact, Hotshot Renegade deals 2 damage to up to one target creature or planeswalker. (You make first contact the first time each turn you cast a spell with a name not in your graveyard or control already.)

Whenever Arisen Rider attacks, creatures your opponents control get -1/-1 until end of turn.
If Arisen Rider or another creature or planeswalker would die, exile it instead.

When this creature enters, surveil 2.
This creature can't be blocked as long as it has a -1/-1 counter on it.

Target creature gets +2/+2 and gains indestructible until end of turn.

Each player exiles up to X cards from their graveyard. Then each player loses life, discards cards and sacrifice creatures equal to X minus the number of cards that player exiled this way.

When Hinasa Historian enters, create a 2/2 colorless Spirit creature token.
Whenever a colorless creature you control enters, you gain 1 life.

Whenever you sacrifice a Clue, you lose life equal to the number of Clues you control, then investigate twice. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Equipped creature gets +2/+2 and has trample.
Equip {2}

When Alenian Cruel-Star enters, put a +1/+1 counter on it if you control another Goblin.

Menace
Revive {1}{R} ({1}{R}, Exile this card from your graveyard: Create a token that's a copy of this card, except it has no mana cost. Activate this ability only any time you could cast a sorcery.)

Enchant creature
When Double Arming enters, put a +1/+1 counter on enchanted creature.
Enchanted creature has menace.
{5}: Return Double Arming to its owner's hand.

When Emberling dies, it deals 1 damage to any target.

When Sandwurm's Might enters, you may have target creature you control fight target creature you don't control.
Each creature you control enters with an additional +1/+1 counter on it.

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

When Cultivator of Crops enters, you may search your library for a basic land or Satrapy card, reveal it, put it into your hand, then shuffle.

Whenever you cast a noncreature spell, put a quest counter on Align the Astrolabe.
At the beginning of your upkeep, create a 1/1 colorless Construct artifact creature token for each three quest counters on Align the Astrolabe.

When Fallen Dynasty Jailer enters, target opponent exiles a card from their hand. When Fallen Dynasty Jailer is no longer on the battlefield, the exiled card's owner puts it on the top or bottom of their library.

Distant Path enters tapped unless you control one or fewer other lands.
{T}: Add {W} or {U}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Menace

Spells cost {3} more to cast this turn.
Activated abilities that aren't mana abilities cost {3} more to activate this turn.

Prowess
Whenever Hethwyr Warcaster or another Wizard you control enters, you may draw a card.

{T}: Add {C}.
{7}, {T}: Copy target instant or sorcery spell with {X} in its mana cost. You may choose new targets for the copy. This ability costs {1} less to activate for each instant and sorcery card in your graveyard.

Draw a card.
If this is the second spell you cast this turn, scry 2. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

Creatures you control gain double strike until end of turn. Whenever a creature you control deals combat damage this turn, put a +1/+1 counter on it.

{T}, Discard a card: Draw a card.