msem-instigator

Flying, lifelink
Creatures entering or leaving the battlefield don't cause abilities to trigger unless that creature is in a pack. (Two or more creatures a player controls with equal power are in a pack.)

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

When Whistling Blades enters, you may destroy target creature or planeswalker.
Recite {1}{B}{B} (You may cast this creature from your graveyard for its recite cost. If you do, exile it when it enters or if it would leave the battlefield.)

When Whiterun Ordainer enters, you gain 4 life.

Voracious 1 (As this enters, you may sacrifice an artifact or creature. If you do, it enters with a +1/+1 counter on it.)
Vigilance, reach

When Wild Entourage enters, create two 1/1 colorless Construct Actor creature tokens.
{4}{G}: Wild Entourage gets +2/+2 and gains trample until end of turn.

When Wild Hermit dies, create a 2/2 white Cat creature token.
Revive—{3}{G}{G}, Sacrifice a creature. ({3}{G}{G}, Sacrifice a creature, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Whenever a creature blocks Wildborn Courtesan, draw a card.
{R}{R}: Untap target creature an opponent controls. That creature blocks Wildborn Courtesan this turn if able.

When Wildsong Summoner enters, shuffle your library, then reveal cards from the top until you reveal a permanent card. Create a token that's a copy of that card, except it's a 3/3 green Beast creature. Put all cards revealed this way on the bottom of your library in a random order.

Flying
When Windrider Elemental enters, target creature gains flying until end of turn.

Flying
When Windwielder enters, you may return target Inscription card from your graveyard to your hand.

Armed — Winterborn Savage gets +1/+1 and has vigilance as long as it's equipped.

When Wise Farseer Chini enters, create a tapped colorless land token named Far-Off Lands with “{T}: Add one mana of any color.”

Flying
When Witch of Spring's Promise enters, shuffle any number of cards from your hand into your library, then draw that many cards plus one.

Deathtouch
At the beginning of your end step, create a 1/1 black Rat creature token with “This creature can't block.”
{1}{B}, {T}, Sacrifice three other creatures: Each opponent discards a card and loses 2 life. You draw a card and gain 2 life.

Flash
When Witch of the Veil enters, if it was cast, you may sacrifice a creature. If you do, return that card to the battlefield under its owner's control.

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.)

{T}: Tap target creature. Activate only if Wizened Veteran is embattled. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

When Wolfbriar Sapling enters, if you control seven or more lands, create a 2/2 green Wolf creature token.

Trample
{5}{G}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)

When Woopip Elder enters, germinate. (Put a +1/+1 counter on a creature or create a 1/1 green Saproling creature token.)

When Woopip Wanderer enters, create two colorless artifact tokens named Lotus Petal with “{T}, Sacrifice this artifact: Add one mana of any color.”
{2}{G}: Germinate. (Put a +1/+1 counter on a creature or create a 1/1 green Saproling creature token.)

Wraith of the Fens gets +2/+2 as long as you've gained life this turn.