msem-instigator

When Rigid Conformist enters, for each {W} spent to cast it, create a 1/1 white Human creature token.
Each creature you control gets +2/+2 if you control another creature with the same name as that creature.

Whenever another creature you control enters, put a +1/+1 counter on it.
Whenever Rilken Preserver attacks, you may exile target nonland permanent you control, then return it to the battlefield under your control.

Flying
Whenever Rivha and at least two other creatures attack, exile all other attacking creatures you control. For each creature exiled this way, create a 3/3 white Angel creature token with flying that's tapped and attacking.

Defender, flying
Ruins Guardian can attack as though it didn't have defender as long as a creature died under your control this turn.
Whenever Ruins Guardian attacks, you may exile two creature cards from your graveyard. If you do, draw a card.

Whenever you make first contact, Runic Enforcer gains lifelink until end of turn. (You make first contact the first time each turn you cast a spell with a name not in your graveyard or control already.)

Shimmer (Whenever this creature attacks, create a tapped and attacking token that's a copy of it. Exile the token at the beginning of the end step.)
When Sandstrider enters, put a +1/+1 counter on target creature.

Flying
Tap three untapped Satrapies you control: Recruit. Activate only as a sorcery. (Create a 0/0 white Soldier Army creature token, then put a +1/+1 counter on each Army you control.)

Vigilance
Seawise Swain gets +1/+1 as long as you control an artifact.
Seawise Swain gets +1/+1 as long as you control an enchantment.

Lionize {1}{W} ({1}{W}, Exile this card from your hand: Put a +1/+1 counter on target creature and it gains the following ability until end of turn. You may cast this card on a later turn from exile.)
Flying

Flying
Sire of Empires gets +1/+1 as long as you control another creature, has lifelink as long as you control an enchantment, and has vigilance as long as you control an artifact.

Flying
Cycling {U} ({U}, Discard this card: Draw a card.)

Flying
As long as you control exactly one other creature, that creature gets +1/+1 and has flying.

Defender
Whenever Slumbering Bear is dealt damage, put a +1/+1 counter on it.
Remove a +1/+1 counter from Slumbering Bear: It can attack as though it didn't have defender this turn.

Lifelink
When you attain Sojourner of the Beyond, create two 1/1 white Spirit creature tokens with flying. They gain haste until end of turn.

When Spoiled Prince enters, each player sacrifices a creature with the greatest power among creatures they control.

Lifelink
{2}{W}: Target Elk gains indestructible until end of turn.

Flying
Vanguard — Whenever a creature you control attacks alone, you may put a +1/+1 counter on it.

Flying
When Stratusform Seraph enters, you may return target creature you control to its owner's hand.

When Sun-Blessed Hoplite enters, target creature you control gets +X/+X until end of turn, where X is your devotion to white. (Each {W} in the mana costs of permanents you control counts toward your devotion to white.)

Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Art of war — At the beginning of your end step, if Teikoku Daimyo dealt damage to an opponent this turn, put a +1/+1 counter on each creature you control that attacked this turn.

Flying

Whenever Twilight Walker perseveres, target creature doesn't untap during its controller's next untap step. (A creature perseveres when it survives damage.)

Disgraced 1 (This enters with a -1/-1 counter. Whenever it deals combat damage to a player, remove all -1/-1 counters from it.)
Attain {3}{W} ({3}{W}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

As long as it's your turn, Vanguard of Glory has first strike.