msem-instigator

Whenever a creature you control perseveres, you draw a card and you lose 1 life. (A creature perseveres when it's dealt damage and doesn't die.)
{1}{B}: Deathmask Initiation deals 1 damage to target creature you control.

Menace
When a card leaves your graveyard, exile the top card of your library. You may play that card until the end of your next turn.

{4}, {T}, Exile Deathwind Detonator: Destroy all nonland permanents. Each player gets an emblem with “At the beginning of your upkeep, you lose 1 life.”

Deathwind Survivor's power and toughness are each equal to the number of enchantments you control.
Whenever an enchantment you control enters, put a +1/+1 counter on target creature.

When Debt Dignitary enters, tap target nonland permanent. That permanent doesn't untap during its controller's untap step for as long as you control Debt Dignitary.

{T}: Put a flood counter on Decanter of Endless Rivers. Add {U} for each flood counter on it.

Decay deals damage to creatures in the form of -1/-1 counters.
{B}{G}: Until end of turn, target creature deals damage to creatures in the form of -1/-1 counters. Activate only if Decay is in your graveyard.

Whenever Deceitful Soul becomes blocked by one or more creatures, it gets +2/+0 until end of turn.

Primal {B}{B} (During your turn, you may cast this spell for {B}{B} instead of playing a land.)
Search your library for a card and put that card into your hand, then shuffle. Exile Deceitful Tutor.

Deception can't be blocked.
{1}{U}{B}: Target creature can't be blocked this turn. Activate only if Deception is in your graveyard.

Creatures you control get +2/+2 and gain vigilance and trample until end of turn.

Indestructible (Damage and effects that say “destroy” don't destroy this creature.)
Whenever Declare, the Mother Bear deals combat damage to a player, put a +1/+1 counter on it.

When Decrepit Hero dies, create a 2/2 black Soldier creature token.
Fleeting {1}{B} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

When Dedicated Waypoint enters, create a 1/1 white Scout creature token.
{T}: Add {R}, {W}, or {B}.

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.
At the beginning of the upkeep of enchanted creature's controller, that player mills a card.

Exile target creature. Return that card to its owner's hand at the beginning of its owner's next end step.

Deep-Sea Terror can't attack unless seven or more cards are in your graveyard.

Flash
Cadence (Whenever you cast a spell, if its mana value is greater than this creature's power, put a +1/+1 counter on this creature.)

As an additional cost to cast Deepmire Abomination, reappropriate or pay {2}. (To reappropriate, exile exactly two cards from your hand and/or graveyard.)
Menace

Defender
Sacrifice two Islands: Deepsea Denizen loses defender until end of turn.

Menace
Creatures you control get +1/+0 as long as you've foretold a card this turn.
Creatures you control get +1/+0 as long as you've cast a foretold spell this turn.

First strike
Whenever a card leaves your graveyard, you may pay {2}{R}. If you do, this creature deals 2 damage to any target.

When this creature enters, you may sacrifice a creature. If you do, create a 4/4 red Horror creature token with menace.

Damage dealt by Deepwater Stinger can't be prevented.

When this creature enters or leaves the battlefield, create a tapped 2/2 black Zombie creature token.