msem-instigator

At the beginning of your upkeep, target player mills two cards. If your main library has five or fewer cards in it, that player mills their library instead.

{2/R}{2/R}: Churning Rough-Roller gets +1/+1 and gains double strike until end of turn.

When Churning Sandwurms enters, remove all counters from target permanent. Put a +1/+1 counter on Churning Sandwurms for each counter removed this way.

When Churning Spellroot enters, create three 1/1 black Worm creature tokens.

Equipped creature has haste.
Sacrifice Cinderblade: Equipped creature gains +2/+2 until end of turn.
Equip {1}

Flying
Whenever Circumspect Flock perseveres, create a 1/1 white Bird creature token with flying. (A creature perseveres when it survives damage.)

Citadel Bagworm gets +0/+1 for each card in your graveyard.
{B}, Discard a card: Switch Citadel Bagworm's power and toughness until end of turn.

{3}{G}: Search your library and/or graveyard for an Aura card, reveal it, and put it into your hand. If you search your library this way, shuffle.
{1}{U}: Untap target creature.

Target creature attacks or blocks this turn if able.
Forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

Armed — Other Goblin creatures you control get +1/+1 and have haste as long as Clanleader of Beragnos is equipped.

Target creature you control gains protection from everything until end of turn.

Whenever you cast an instant or sorcery spell, you may exile that card instead of putting it anywhere else as it resolves.
At the beginning of your upkeep, Clash Reactor deals X damage to each opponent, where X is the number of colors of cards exiled with Clash Reactor.

Clash at Geier Reach deals 2 damage to each opponent and to each creature and planeswalker they control.
Cycling {2} ({2}, Discard this card: Draw a card.)

Target creature fights another target creature. (Each deals damage equal to its power to the other.)

Whenever a creature enters under an opponent's control, you may have that player lose 1 life.
Unveil {2}{B}{R} ({2}{B}{R}: Transform this. Unveil only as a sorcery.)

This spell costs {1} less to cast for each card you've discarded this turn.
Draw three cards.

Sacrifice a creature: Surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)

This spell costs {1} less to cast for each creature you attacked with this turn. (Those creatures don't have to still be on the battlefield.)
Flying

Target creature you control gets +1/+1 until end of turn. It deals damage equal to its power to target creature you don't control.

Whenever you cast an instant or sorcery spell, Clever Infiltrator gets +2/+0 until end of turn and can't be blocked this turn.

Whenever you cast a noncreature spell, you may shuffle target card an opponent owns in exile into its owner's library.

{T}, Tap an untapped creature you control: Choose one —
• Add one mana of any color.
• Target player loses 2 life.
• Target player gains 3 life.
• Target player mills four cards.

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.)
Tap four untapped creatures you control: Unlock Clockwork Astrolarium. If the revealed card is white, put it into your hand. Otherwise, put it on top of your library.

When Cloister enters, exile another target nonland permanent you control and target nonland permanent you don't control until Cloister leaves the battlefield.
{2}{W}, Sacrifice Cloister: You gain 5 life.

Trample
You may spend black and green mana as though it were mana of any color.
Whenever Closing-Act Abomination attacks, look at the top X cards of your library, where X is the number of colors among cards in your graveyard. Put up to one of them into your hand and the rest on the bottom of your library in a random order.