msem-instigator

Whenever you scry, put a +1/+1 counter on Dunesea Cartographer for each card you looked at while scrying this way.
{3}{W}{U}: Scry 2.

Whenever Dunesea Dreadstalker or another nontoken creature you control dies, amass Soldiers 1. (Put a +1/+1 counter 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.)

When Dunesea Merchant enters, tap up to X target creatures, where X is the number of Satrapies you control.
Satrapycycling {2} ({2}, Discard this card: Search your library for a Satrapy card, reveal it, put it into your hand, then shuffle.)

Reach
{T}: Add one mana of any color. Spend this mana only to cast an Azra or Demon spell, and that spell can't be countered.

Vigilance, ward {2}
{1}{G}, {T}: Put a +1/+1 counter on Dunetreader Tortoise. Activate only as a sorcery.

Copy target spell. You may choose new targets for the copy. (A copy of a permanent spell becomes a token.)

Flash
When Duplicated Dismantler enters, if you cast another spell this turn, return target spell to its owner's hand.

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

Protection from Dawn Chord (This creature can't be blocked, targeted, dealt damage, or enchanted by anything named Dawn Chord.)
{1}{R}: Target Reflection's base power becomes equal to Dusk Chord's power until end of turn.

Whenever Dusk Insurgent perseveres, create a 1/1 white Warrior creature token. (A creature perseveres when it survives damage.)

When Dusk Lieutenant enters, forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)
Once each turn, when you discard a card during your turn, each opponent discards a card.

Vision (Whenever this or another creature you control enters, reveal the top card of your library. Then you may put that card into your graveyard.)
Whenever Dusk Occultist envisions a creature card, draw a card.

Lifelink
{W}{B}, {T}: Dusk Rider deals X damage to target attacking creature, where X is the number of Spirits you control.

Improve {1}{B} ({1}{B}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
Once each turn, when you gain life, you may have each opponent loses 1 life.

When Duskling Stalker dies, if it didn't have any counters on it, return it to the battlefield with your choice of a deathtouch, lifelink, or +1/+1 counter on it.

Poisonous 1 (Whenever this creature deals combat damage to a player, that player gets a poison counter.)
Duskscale Marauder can't be blocked.

Whenever Duskwatcher attacks, create a Function token with “Tap target creature.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Landfall — Whenever a land you control enters, target creature you control gains vigilance until end of turn.

Each other nontoken Elf and/or Warrior you control enters with an additional +1/+1 counter on it.
{G}{G}, {T}, Remove two +1/+1 counters from among creatures you control: Create two 1/1 green Elf Warrior creature tokens.

Landfall — Whenever a land you control enters, Duskwood Vanguard gets +1/+1 until end of turn.

Landfall — Whenever a land you control enters, you may pay {1}{G}. If you do, create a 2/2 green Wolf creature token.

{T}: Target player mills a card.
{4}, {T}, Exile Dusty Record: Target player shuffles their graveyard into their library.

When Dutiful Camel enters, put a +1/+1 counter on target creature you control.

Dutiful Chasqui gets +2/+1 as long as you control two or more other creatures that share a name with it.
A deck can have any number of cards named Dutiful Chasqui.