msem-instigator

When Drown in Apathy enters, exile target creature until Drown in Apathy leaves the battlefield. If a permanent would be returned to the battlefield this way, put it in its owner's hand instead.

All creatures get -2/-2 until end of turn. Scry 1.

Whenever you cast a blue spell, you may cast creature spells this turn as though they had flash.
Whenever you cast a black spell, put up to one target card from your graveyard on top of your library.

When Drownyard Scavenger enters, each player may return an instant or sorcery card from their graveyard to their hand.

Reach

Haste
Ward—Pay 3 life.
{R}, Tap an untapped artifact you control: Drysand Mole gets +1/+0 until end of turn. Up to one target creature can't block it this turn.

When Dthan's Daggers enters, you may attach it to target creature you control.
Whenever equipped creature attacks, it gets +3/+0 and gains first strike until end of turn.
Equip {3}{R}

Menace, haste
Whenever another creature dies, you get a blood counter.
{B}{R}, Pay two blood counters: Return Dthan, Who Bloodies the Sands from your graveyard to the battlefield.

Lifelink
If you would gain life, you gain that much life plus 1 instead.

Counter target spell.
Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, that spell's controller reveals their hand. You may exile a nonland card from that player's hand. If you do, that player draws a card.

{2}: Duela Duelist gains first strike until end of turn.
{3}: Duela Duelist gains distorted until end of turn. (This creature can be blocked by tapped creatures but not untapped creatures.)

Whenever you cast a spell with mana value 4 or greater, catalyze. (The next spell you cast this turn costs {1} less to cast.)

Whenever you cast an instant or sorcery spell, you may untap Duela Science Kit.
{T}, Tap an untapped creature you control: Catalyze. (The next spell you cast this turn costs {1} less to cast.)

Deathtouch
At the beginning of each opponent's upkeep, that player loses 1 life.

{3}{R}: Target creature can't be blocked this turn if it's an artifact creature or has power 2 or less.

Enchant creature
Enchanted creature gets +2/+2 and can't be blocked as long as defending player controls a Desert.

Flying
When Dune Wraith enters, distribute two +1/+1 counters among Spirits you control.

At the beginning of your upkeep, choose one —
• Create a colorless artifact token named Etherium Cell with “{T}, Sacrifice this artifact: Add one mana of any color.”
• Put a +1/+1 counter on another target artifact. It becomes a 0/0 Construct artifact creature if it isn't a creature.

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.)

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

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.

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.

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.)