msem-instigator

Flash
Improve {W} ({W}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
You may activate equip and improve abilities any time you could cast an instant.

Warm Blood Chaser has flying and haste as long as you control a Goblin.

First strike
Wither (This deals damage to creatures in the form of -1/-1 counters.)

Changeling (This card is every creature type.)
Watcher of the Polyps has all names of creature cards in addition to its name as long as it's on the battlefield.
Watcher of the Polyps gets +X/+X, where X is the greatest number of creatures you control with the same name.

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

Whenever a creature in Water Sutra Daoshi's pack dies, return a creature card with lesser mana value than that creature from your graveyard to your hand. (Two or more creatures you control with equal power are in a pack.)

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.

When Weald Wanderer enters the battlefield, you gain 3 life and each opponent loses 2 life.
{1}, Pay 1 life: Shuffle Weald Wanderer into its owner's library. If you do, draw a card.

When Weary Adventurer enters the battlefield, return a permanent you control to its owner's hand.

When Weathered Pilgrim enters the battlefield, return target card from your graveyard to your hand.

Whenever Weathered Skiff attacks, it gets +1/+1 until end of turn.
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Ship Vehicle becomes an artifact creature until end of turn.)

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
When Weathered Veteran dies, you may put a -1/-1 counter on target creature.

Reach
Erratic (When this creature dies, reveal the top four cards of your library. Put a creature card that costs less than this revealed this way onto the battlefield and the rest on the bottom of your library in any order.)

At the beginning of your upkeep, discard a card and create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)

When Weeping Yaoguai enters the battlefield, create a 1/1 colorless Spirit creature token.
Scavenge {3}{B} ({3}{B}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

Put two +1/+1 counters on up to one target creature.
Coalesce {6}{G}{G} (You may cast this from your graveyard for its coalesce cost. If you do, put it onto the battlefield as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Flying
Welkin Tern can block only creatures with flying.

Whenever West Ward Purifier becomes tapped, you gain 1 life.

Flash
Heretic (Whenever you cast a spell that doesn't share a color with this creature, it gets +1/+1 until end of turn.)

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

When Whisper Witch enters the battlefield, choose up to one target creature. That creature's controller mills four cards, then puts that creature on top of their library.

Menace (This creature can't be blocked except by two or more creatures.)

Prowess, haste
Mirage {R} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Vigilance