msem-instigator

When Commander of the Cavalry enters the battlefield, you may search your library for a creature card with ride, reveal it, and put it into your hand. If you do, shuffle.
{X}, {T}: Put a creature card with ride and mana value X or less from your hand onto the battlefield transformed and attached to another target creature you control without a Steed attached to it.

Creature tokens you control get +1/+1.
{3}{W}: Create a 1/1 white Warrior creature token.

Flash
When Commanding Princess enters the battlefield, choose two —
• Commanding Princess deals 2 damage to any target and you gain 2 life.
• Return target permanent card with mana value 2 or less from your graveyard to your hand.
• Destroy target artifact or enchantment.
• Create a 1/1 colorless Shapeshifter creature token with changeling.

When Compulsory Studies enters the battlefield, exile target creature until Compulsory Studies leaves the battlefield. Each player draws a card.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Whenever Conchhorn Shinygrabber attacks, you may pay {1}. If you do, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)
{W}{U}{B}{R}{G}: Conchhorn Shinygrabber gets +3/+3 and gains lifelink until end of turn.

When Condemned Cavalier enters the battlefield, create a white and black Aura Curse enchantment token named Profane March attached to target player. The token has enchant player and “Whenever a creature enchanted player controls attacks, that player loses 1 life and defending player gains 1 life.”

Whenever you cast an enchantment spell, create a 1/1 white and black Bird creature token with flying and vigilance.
Whenever three or more creatures you control deal combat damage to a player, that player sacrifices a creature. If they can't, they discard a card.

Other Knight creatures you control get +1/+1.

When Confining Priest enters the battlefield, exile another target creature with power 4 or less until Confining Priest leaves the battlefield. (That creature returns under its owner's control.)

Vigilance
Conflict Capturer gets +2/+0 as long as a permanent you controlled left the battlefield this turn.

When Conflux Ravager enters the battlefield, destroy target nonland permanent an opponent controls.
Cycling {2} ({2}, Discard this card: Draw a card.)

Whenever you cast an Aura spell, nourish 1. (To nourish 1, either put a +1/+1 counter on this creature or create a 1/1 white Citizen creature token.)

When Conquerer's Blade enters the battlefield, create a 1/1 white Soldier creature token and attach Conquerer's Blade to it.
Equipped creature gets +1/+0 and has first strike.
Equip {3}

Create three 1/1 white Soldier creature tokens. Scry 3.

(As this Discovery enters and after your draw step, add a progress counter. Stop after you've discovered.)
I, II — Create a 1/1 white Soldier creature token with vigilance.
Discovery — At the beginning of combat on your turn, you may pay {2}{W}. If you do, creatures you control get +1/+1 until end of turn.

Lifelink
Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)

Machinate — {T}, Tap another untapped artifact you control: Exile target artifact or creature, then return that card to the battlefield tapped under its owner's control.

Advance {2}{W} (Cast this for {2}{W} to advance it as it enters. {2}{W}: Advance this as a sorcery.)
Whenever Construct Engine advances, create a 1/1 colorless Construct artifact creature token.

Constructed Jay is all colors.
Constructed Jay gets +1/+0 and has flying as long as you control three or more Satrapies.

Scry 2, then draw two cards. You gain 2 life.
Monument {2}{W}{U} (You may cast this transformed from your graveyard for its monument cost. Exile it if it would leave the battlefield or not resolve.)

Enchant creature
Enchanted creature gets +1/+3.
{W}: Return Conviction to its owner's hand.

Level experience (Whenever this creature attacks, if it has fewer than three level counters on it, put a level counter on it.)
When Copperhide Calf has three or more level counters on it, remove them all and transform it. [2/2]
[level 1-3] Prevent the first 1 damage that would be dealt to Copperhide Calf each turn. [3/3]

Exile target creature with power 4 or greater.
Create a Treasure token. (It's an artifact with “{T}, Sacrifice this permanent: Add one mana of any color.”)

When Coralight Champion enters the battlefield, create a white Aura enchantment token named Hila's Favor attached to target creature. The token has enchant creature and “Enchanted creature has double strike as long as there's another Aura attached to it. Otherwise, it has first strike.”

{3}{W}: Tap target creature. Activate only during your turn.