msem-instigator

Creatures you control dying cause abilities of that creature to trigger as though that creature entered the battlefield.
{2}{W}{B}, Sacrifice another creature: Destroy target nonland permanent.

Tyrant of the Depths has hexproof as long as it's untapped.
Whenever you cycle Tyrant of the Depths or it attacks, tap target nonland permanent you don't control and put a stun counter on it.
Basic landcycling {1}{U} ({1}{U}, Discard this card: Search your library for a basic land card, reveal it, and put it into your hand, then shuffle.)

If a creature card would be put into an opponent's graveyard from anywhere, instead exile it, then copy it. You may cast the copy. (You still pay its costs, including color. Copies of permanents enter the battlefield as tokens.)

Hexproof
When Uncharted Leviathan enters the battlefield, target creature can't be blocked this turn.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)

Undine Coven gets +1/+1 for each other Merfolk you control.
Whenever you cast a noncreature spell, Undine Coven deals 1 damage to target player or planeswalker.

Trample
Whenever Unruly Cannoneer crews a Vehicle, that Vehicle gets +1/+1 and gains trample until end of turn.

First mate—There are four or fewer different mana costs among nonland cards in your starting deck. (If this card outside the game is your chosen first mate, you may swap it with a card in your opening hand.)
First strike
Each spell your opponents cast that would cost less than three mana to cast costs {1} more to cast.

Whenever Veiled Charmer attacks, target creature blocks it this turn if able.

Veiled Merfolk can't be blocked by creatures with greater power.
When Veiled Merfolk enters the battlefield, mill a card.

{T}: Add {C}. Spend this mana only to cast an instant or sorcery spell or activate an ability.
{2}{U}: Move a counter from target creature onto another target creature.

Defender
Venerable Loremaster can attack as though it didn't have defender if it's in a pack. (Two or more creatures you control with equal power are in a pack.)

({T}: Add {B}, {G}, or {U}.)
Verdant Dominion enters the battlefield tapped.

When Volaris Tideshaper enters the battlefield, look at the top four cards of your library. Put one of those cards into your hand. and the rest on the bottom of your library in a random order.
Whenever you cast a noncreature spell, Volaris Tideshaper can't be blocked this turn.

Whenever Wakeborne Kraken or another Kraken, Leviathan, Octopus, or Serpent enters the battlefield under your control, you may return target creature an opponent controls to its owner's hand.
Whenever a creature an opponent controls leaves the battlefield, if it didn't die, draw a card.

Whenever Waketide Serpent attacks, you may pay {2}{U}. If you do, tap target creature. It doesn't untap during its controller's next untap step.

When Ward-Lost Hermit enters the battlefield, mill three cards.
{2}, {T}, Sacrifice Ward-Lost Hermit: Return target instant or sorcery card from your graveyard to your hand.

Vigilance
Whenever Watchful Navigator crews a Vehicle, that Vehicle gets +1/+1 and gains vigilance until end of turn.

Each other creature you control that's a Merfolk or an Elemental gets +1/+1.
Whenever you cast an instant, sorcery, or Merfolk spell, you may pay {1}. If you do, create a 1/0 blue Elemental creature token.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
{3}{U}: Target creature gains slipstream until end of turn.

Whenever Wavering Sorcerer attacks, you may switch its power and toughness until end of turn.
Unveil {3}{U}{R} ({3}{U}{R}: Transform this. Unveil only as a sorcery.)

Whenever two or more creatures you control deal combat damage to a player, you lose 1 life and draw a card.

Whenever you cast a spell, you may pay {1}. If you do, Wizened Tortle explores. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then you may put that card in your graveyard.)

Haste
When Wretched Merfolk enters the battlefield, target creature can't block this turn.