msem-instigator

Whenever you draw a card, put a hatch counter on Reefcrown Egg.
{T}, Sacrifice Reefcrown Egg: You may put a creature card with mana value less than or equal to the number of hatch counters on Reefcrown Egg from your hand onto the battlefield.
Cycling {2} ({2}, Discard this card: Draw a card.)

First strike, trample
Whenever Regal Coralhorn deals combat damage to a player or planeswalker, return target card with a cycling ability from your graveyard to your hand.
Cycling {2} ({2}, Discard this card: Draw a card.)

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
As long as you control three or more artifacts, Regal Seasnake has vigilance. (Attacking doesn't cause it to tap.)

Target instant or sorcery card in your graveyard gains flashback until end of turn. Its flashback cost is equal to its mana cost.
Flashback—{R}, Discard a card. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Mill three cards. Return a card from among the milled cards to your hand. Then shuffle three cards from graveyards into their owners' libraries.

Flash
When Remnant Spotter enters, put target permanent card from your graveyard on top of your library.

Enchant creature
Enchanted creature gets +2/+2 and attacks each turn if able.

Destroy target creature.

Return target permanent card from your graveyard to your hand. You gain 3 life.

Enchant creature
Enchanted creature can't attack, block, or crew Vehicles.

Codex — Ser Wayver, the Broken Hour; Suzume Oshiruko; Aguri, Shadow of Doubt; Sukhar, Consort to the Dark; Chi Lee of the Underworld. (As this enters, conjure its contents into a shuffled face-up additional library.)
You may spend mana as though it were mana of any color to cast this codex's contents.

Choose one —
• Rip Apart deals 3 damage to target creature or planeswalker.
• Destroy target artifact or enchantment.

Concord — When Riptide Mystic enters, if there are four or more card types among permanents you control, you may return target nonland permanent to its owner's hand.

Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
Madness {1}{G} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Spirited (When this creature enters, you may activate one of its activated abilities without paying its costs.)
{1}{R}, Discard a red card: Roggar deals 2 damage to any target. This damage can't be prevented.
{2}{R}, Exile a red card from your graveyard: Create two tapped 1/1 red Elemental creature tokens.

Target opponent looks at the top six cards of your library and separates them into a face-down pile and a face-up pile. Choose a pile, then play any number of cards from it without paying their mana costs. Put the rest of the cards into your graveyard.

Choose one —
• Counter target spell unless its controller pays {2}.
• Create a tapped token that's a copy of target token you control.

{1}{G}, {T}, Discard a card: Another target creature you control gets +X/+X until end of turn, where X is 4 minus that creature's power.

Whenever Roving Dreadnought attacks, you may salvage a card that was put into your graveyard this turn. (Exile one 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.)

Until end of turn, target creature you control gets +2/+0 and gains “When this creature dies, mill two cards, then return it to the battlefield under its owner's control.”

Haste
Ruin Shark attacks each turn if able.
Ruin Shark gets +1/+0 and has first strike as long as you've drawn two or more cards this turn.

{1}, Sacrifice Ruinous Proselyte: Destroy target artifact or nonbasic land.

When Rum Guzzler enters, forebode, then you lose 1 life. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

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.
Madness {3}{G} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Rustshell Crustacean gets +1/+1 for each artifact you control.
Whenever Rustshell Crustacean attacks, choose one —
• Search your library for an Equipment card, reveal it, and put it into your hand, then shuffle.
• Create a Treasure token.