msem-instigator

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.

At the beginning of your end step, if you cast no spells this turn, you may return Wrathful Meditant to its owner's hand.

Colossal 2—{4}{B}{B} (You may cast this for its colossal cost to have it enter with two +1/+1 counters; or pay {4}{B}{B} as a sorcery: Put two +1/+1 counters on it if it has none.)
Menace
When Wretched Catoblepas's colossal ability puts one or more counters on it, each opponent sacrifices a creature.

Flying
Assault {2}{B} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
When Wretched Lammasu assaults, each opponent discards a card.

Whenever an enchantment you control enters, draw a card.

Renown 2 (When this creature deals combat damage to a player, if it isn't renowned, put two +1/+1 counters on it and it becomes renowned.)
Each creature you control with a +1/+1 counter on it has indestructible.

Whenever one or more creatures you control deal combat damage to a player or planeswalker, put a +1/+1 counter on target creature you control.

When Yamisaran Guard enters, create a colorless Equipment artifact token with “Equipped creature gets +1/+1” and equip {1}.

Other enchantment creatures you control get +1/+1.
As long as you control three or more enchantment creatures, if a triggered ability of an enchantment you control would trigger, that ability triggers an additional time.

Deathtouch
Inspired — Whenever Yenzu Nightblade becomes untapped, target creature you control gets +1/+1 and gains deathtouch until end of turn.