msem-instigator

Juvenile Boa gets +2/+0 as long as you control a legendary creature.

When Project Head enters, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
{2}{U}, Exile Project Head: Shuffle your hand and graveyard into your library, then draw seven cards. Activate only if you control seven or more artifacts.

Return up to one target creature to its owner's hand. Draw a card.
Tether (Then if you cast this from your hand, you may exile it tethered to a creature you control. When it dies, you may cast this from exile without paying its mana cost.)

Motivate 3 (When this creature enters, you may motivate target creature with lesser power than this by putting three +1/+1 counters on it.)
At the beginning of combat on your turn, you may have target creature you control gain vigilance until end of turn.

Reach
Whenever another creature you control becomes the target of an instant or sorcery spell, that creature gets +3/+3 until end of turn.

Menace, prowess

(As an Encounter enters, choose an opponent to protect it. You and others can attack it. When defense counters are removed, create a 0/0 Army token if you don't control one, then put that many +1/+1 counters on a Army you control.)
When Crisis in Soli enters, amass Soldiers 3. (Put three +1/+1 counters on an Army you control. It's also a Soldier. If you don't control one, create an 0/0 black Soldier Army creature token first.)

Choose one —
• Target creature gets +2/-1 until end of turn.
• Basat Charm deals 3 damage to target player or planeswalker.

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

Equipped creature has indestructible as long as it's your turn.
Whenever equipped creature attacks, it gets +X/+0 until end of turn, where X is its power.
Equip {6}

Equipped creature gets +3/+2.
Whenever a land you control enters, you may attach Axe of the Crann to target creature you control.
Equip {4}

Each player chooses a nonland permanent they control, then sacrifices the rest.

When Lady Ilyrana Jhalach enters, create two 1/1 black and green Elf Warrior creature tokens with reach.
{G}, Tap an untapped Elf you control: Target Elf creature gets +2/+2 until end of turn.
{1}{B}, Tap two untapped Elves you control: Target non-Elf creature gets -2/-2 until end of turn.

When The Third Breach enters, discard your hand, then draw seven cards.
Creatures you control get +3/+3, have haste, and are Horrors in addition to their other types.
At the beginning of each end step, sacrifice each creature you control.

Whenever a land you control enters, target creature gains your choice of flying or lifelink until end of turn.

(As an Encounter enters, choose an opponent to protect it. You and others can attack it. When defense counters are removed, create a 0/0 Army token if you don't control one, then put that many +1/+1 counters on a Army you control.)
When Danaj Rising enters, target player reveals their hand. You choose a nonland card from it. That player discards that card. You lose 1 life.

When Chaotic Pupil enters, harmonize twice. (To harmonize, trigger up to one harmony of a permanent you control.)
Harmony — Draw a card, then discard a card.

Up to three target creatures can't block this turn.
Menagerie — If there are five or more creature types among creatures you control, exile the top three cards of your library. You may play one of those cards until the end of your next turn.

Choose two —
• Put two +1/+1 counters on target creature.
• Atieh's Command deals damage to any target equal to the greatest power among creatures you control.
• You gain life equal to the greatest power among creatures you control.
• Draw cards equal to the greatest power among creatures you control, then discard three cards.

Lifelink
Effigy of Morality gets +1/+1 as long as your fealty to Plains is four or greater. (Each Plains you control counts towards your fealty to Plains.)

Vigilance, trample
Whenever you draw your second card each turn, put a +1/+1 counter on Coralblade Cohort.
Cycling {G} ({G}, Discard this card: Draw a card.)

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Iridescent Familiar enters, if you control another creature with flying, draw a card.

Transcend (Activate as a sorcery to gain the next type and a +1/+1 counter.)
Ward—Discard a card.
{B}{R}: Demigod — Draw a card, then discard a card. You may have each opponent sacrifice a nonland permanent with the same mana value as the discarded card.
{4}{B}{R}: God — Create two tokens that are copies of Shi Hou's back face.

Target creature gets -3/-3 until end of turn.

When Young Chasqui enters, if you cast it, reveal the top five cards of your library. Put any number of creatures named Young Chasqui from among them into your hand. Put the rest of the revealed cards on the bottom of your library in a random order.
A deck can have any number of cards named Young Chasqui.