msem-instigator

(Add a quest counter as this enters. Sacrifice after 3.)
Whenever you attack, add a quest counter.
1 — Create a 0/1 white Human creature token named Lost Child.
Scry 2.
2, 3 — Exile a token you control named Lost Child. If you do, create two 1/1 white Soldier creature tokens and you gain 4 life.

As long as a creature you control has flying, creatures you control have flying. The same is true for first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, reach, trample, and vigilance.

Primal {W} (During your turn, you may cast this spell for {W} instead of playing a land.)
Destroy target attacking or blocking creature.

Enchant creature
Enchanted creature gets +2/+2.
When Seeking Horizons is put into your graveyard from anywhere other than your library, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Spirited (When this creature enters the battlefield, you may activate one of its activated abilities without paying its cost.)
{2}{W}: Create a 1/1 white Human Samurai creature token.

When Seikatsu Warleader enters the battlefield, if it's not a token, create a token that's a copy of target creature token you control.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever a +1/+1 counter is put on Sejiri Skyhunter, it gains flying until end of turn.

Create a 1/1 colorless Construct artifact creature token. If you control an artifact, create two of those tokens instead.

When Seluriel's Blessing enters the battlefield, put a +1/+1 counter on each creature you control.
Creatures you control enter the battlefield with an additional +1/+1 counter on them.
Creatures you control with counters on them have vigilance and indestructible.

[+1]: You gain 1 life. Put a +1/+1 counter on up to one target creature.
[–3]: Exile target creature. Its controller gains life equal to its power.
[–8]: You get an emblem with “Creatures you control get +1/+1 and have double strike and lifelink.”

When you cast Senaturian Centurion, reveal cards from the top of your library until you reveal a creature card with mana value 2 or less. Copy that card, then put the revealed card into your hand. You may cast the copy without paying its mana cost. Put the revealed cards on the bottom of your library in a random order.

Senaturian Legion gets +1/+1 for each other creature on the battlefield named Senaturian Legion.
A deck can have any number of cards named Senaturian Legion.

When Sending Stones enters the battlefield, harmonize twice. (To harmonize, trigger up to one harmony of a permanent you control.)
If you would harmonize, you may trigger a harmony of a permanent card in your graveyard instead.

Choose one —
• Target permanent gains protection from instants and sorceries until end of turn.
• You gain 3 life.
• Draw a card.

Equipped creature gets +2/+0. As long as it's a Knight, it has first strike.
Equip {1}{W}

Whenever Sentry of Kollis Gate is dealt damage, put a +1/+1 counter on each other creature you control.

Flying
When Seraph of Renewal leaves the battlefield, you may return target permanent card with mana value 3 or less from your graveyard to the battlefield.

Flying, vigilance, lifelink
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Flying
Whenever you cycle Seraph of the Stage or it attacks, audition for white. (Create a 1/1 Construct Actor creature token, a Scout Role giving 2/3 and vigilance, or a Cleric Role giving 2/2 and lifelink. Roles replace older ones.)
Basic landcycling {1}{W} ({1}{W}, Discard this card: Search your library for a basic land card, reveal it, and put it into your hand, then shuffle.)

Prevent all damage target spell or permanent would deal this turn. You gain life equal to the damage prevented this way.

Vanishing 10 (This permanent enters the battlefield with ten time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
If you would lose 1 or more life other than to pay a cost, instead remove that many time counters from Serene Prayer. (If you would lose more life than there are time counters on Serene Prayer, the life loss is still prevented.)

Enchant creature
Enchanted creature can't attack.
Civilized — Enchanted creature can't block and its activated abilities can't be activated if you control an artifact, a creature, and an enchantment.

[+1]: Distribute two +1/+1 counters among any number of target creatures you control.
[–1]: Create two 1/1 white Monk creature tokens.
[–6]: Until your next turn, you choose which creatures attack or block and how those creatures attack or block.

[+1]: Create a 1/1 white Warrior creature token with lifelink. You gain 1 life.
[–2]: Put two +1/+1 counters on target creature. It gains double strike until end of turn.
[–7]: Choose up to three creatures, then destroy the rest.

As long as it's your turn, Seto San is a 3/3 Human Warrior creature with indestructible.
[+1]: Up to one target creature you control gains lifelink until end of turn.
[0]: Create a 1/1 white Warrior creature token.
[–X]: Search your library for an Aura or Equipment card with mana value X and put it onto the battlefield, then shuffle.