msem-instigator

When Warrior of the Folded Fan dies, invigorate 2. (Choose a creature with the least power among creatures you control and put two +1/+1 counters on it.)

Trample, prowess
You may exert Wartorn Veteran as it attacks. When you do, double its power until end of turn. (An exerted creature won't untap during your next untap step.)

Hexproof
When Wary Watchkeeper enters, target player mills three cards.

Advance {3} (Cast this for {3} to advance it as it enters. {3}: Advance this as a sorcery.)
Whenever Wastes Scrambler advances, put your choice of a +1/+1, first strike, menace, trample, or vigilance counter on it. If {R}{W}{B} was spent to advance it, repeat this process twice.
Crew 1

Whenever Wasting Soul attacks or blocks, sacrifice a creature, then put two +1/+1 counters on Wasting Soul.

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
Bulwark — {1}{W}, {T}: Create a 1/1 white Soldier creature token. Activate only if you control a creature with toughness 4 or greater.

Flying

Flying (This creature can't be blocked except by creatures with flying or reach.)
Vigilance (Attacking doesn't cause this creature to tap.)

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 Wavebreaker enters, add two mana of any one color. You can't spend this mana to cast spells.

Flying
Whenever another creature you control enters, you may have Waxing Celestial get +1/+1 until end of turn.

Whenever you gain life, put a +1/+1 counter on Wayfaring Pilgrim.

When Wayfaring Realmstitcher enters, you may search your library for a basic land card, reveal it, put it into your hand, then shuffle.

When Wayfaring Swindler enters, destroy all permanents attached to target creature.

When Weald Sentry enters, search your library for a basic land card, reveal it, put it into your hand, then shuffle.
When Weald Sentry dies, draw a card.

{T}, Exert Weary Border Guard: Tap target creature. (An exerted creature won't untap during your next untap step.)

Haste
Whenever Weary Sentinel attacks, you may pay {2}{R}{W}. If you do, it gets +2/+0 and gains first strike until end of turn.

{2}{R}: Creatures you control get +1/+0 until end of turn.
{1}{G}: Creatures you control gain trample until end of turn.

Whenever Weaver of Lore attacks, you may reveal your hand. Weaver of Lore gets +2/+2 until end of turn if you reveal two or more blue cards this way.

Whenever an enchantment you control enters, target opponent loses 1 life and you gain 1 life.

Vision (Whenever this or another creature you control enters, reveal the top card of your library. Then you may put that card into your graveyard.)
Whenever Weaver of the Winds envisions an instant or sorcery card, draw a card.

When Weedy Wanderer leaves the battlefield or phases out, put a +1/+1 counter on a creature you control.

Deathtouch
Each opponent's maximum hand size is reduced by the number of poison counters that player has.

When Weeping Yaoguai enters, 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.)