msem-instigator

Target attacking creature gains double strike until end of turn. Arm it. (Create a colorless Equipment artifact token with “Equipped creature gets +1/+0” and equip {2}, then attach it to that creature.)

Whenever War Priest of Bahet deals combat damage to a player, purge. (Exile two cards that share a type from graveyards. If you do, draw a card.)

When War of Resources enters, recruit. (Create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)
Whenever a creature you control dies, each opponent loses 1 life.

War-Pride Champion can't be blocked by creatures with power 2 or less.
Stampede — Whenever War-Pride Champion and a creature with greater power attack, target creature you control gets +2/+2 until end of turn.

Glorious end — When Warband Commander dies, if it was tapped, put a +1/+1 counter on each creature you control that attacked this turn.

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

Warden of the Fronds' power and toughness are each equal to the number of Forests you control.
Warden of the Fronds has indestructible as long as you control five or more lands.

Lifelink
{3}{W}: Exile Wardens of the Ulek. Return it to the battlefield under its owner's control at the beginning of the next end step.

Whenever Warhound Shuja attacks, look at the top three cards of your library. You may put a creature card with mana value less than or equal to Shuja's power from among them onto the battlefield tapped and attacking. Put the rest on the bottom of your library in any order.

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

Each instant and sorcery card in your graveyard gains agonize until end of turn.
Agonize (You may cast this card from your graveyard by putting a -1/-1 counter on a creature you control in addition to paying its other costs. Then exile this card.)

As Warmonger Contraption enters, choose a creature type.
Warmonger Contraption is the chosen type in addition to its other types.
Warmonger Contraption's power and toughness are each equal to the number of creatures of the chosen type you control.

Flying, lifelink

You may pay {0} rather than pay the glitch cost for spells you cast.
Whenever you cast a glitched spell, Warped Glitchmage deals 1 damage to target opponent.

Warped Recluse can't be blocked by creatures with greater power.
Whenever Warped Recluse attacks and isn't blocked, exile target creature defending player controls. At the beginning of that card's owner's next upkeep, return it to the battlefield under their control.

When Warping Relic enters or is put into a graveyard from the battlefield, choose one —
• Draw two cards, then discard a card.
• Return another target nonland permanent to its owner's hand.
• Choose any number of target creatures. Switch their power and toughness until end of turn.

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.)

When Warrior's Perspective enters, invigorate 1. (Choose a creature with the least power among creatures you control and put a +1/+1 counter on it.)
Whenever a creature you control with a +1/+1 counter on it becomes tapped, you may draw a card. If you do, discard a card.

Creatures you control get +1/+0 and attack each turn if able.
As long as you control four or more Mountains, attacking creatures you control get an additional +1/+0 and have first strike.

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

Whenever Watch Me Burn enters or another source you control deals noncombat damage, put an ignition counter on Watch Me Burn. Then it deals damage equal to the number of ignition counters on it to each opponent.

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.