msem-instigator

Doom deals 3 damage to any target and you gain 3 life.
Reconstruct {3}{B}{B} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)
You may cast Doom from exile by paying {4}{B}{B}{B} rather than its mana cost. If you do, shuffle it into your library instead of putting it anywhere else as it resolves.

When Doom Cultist dies, target player loses 2 life and you gain 2 life.

Target creature you control gains deathtouch until end of turn. It fights another target creature.

Pressure {3}{U}{B} (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
Destroy up to one target creature. Return all other nonland permanents to their owners' hands.

Flying, first strike, haste
Whenever Doombringer Dragon attacks, you may sacrifice another creature. If you do, Doombringer Dragon gets +3/+0 until end of turn.

Haste
When Doomed Alchemist dies, create two Treasure tokens. (They're artifacts with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Deathtouch
When Doomed Explorer dies, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Vanishing 4 (This permanent enters with four time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
When Doomed Fate leaves the battlefield, if it had no time counters on it, destroy all nonland permanents.

Enchant creature
Enchanted creature gets -2/-2.
At the beginning of the upkeep of enchanted creature's controller, that player discards a card.

Menace
When Doomed Questant enters, each opponent sacrifices a creature and discards a card.

When Doomed Traveler dies, create a 1/1 white Spirit creature token with flying.

When Doomed Widow dies, create a 1/1 white Spirit creature token with flying.

When Doomed Woodsman dies, create a 1/1 green Faerie Druid creature token with hexproof.

Whenever Doomsower or another Human you control dies, you draw a card and you lose life equal to that creature's power.

When Doomstep Giant enters, each player sacrifices a land.

Whenever you cast your second spell each turn, you may have Dormant Memory phase out until you cast your second spell in a turn. (While phased out, treat it and anything attached to it as though they don't exist.)
Fleeting {1}{U} (You may cast this spell for its fleeting cost. If you do, sacrifice it at the beginning of the next end step.)

Enchant creature
When Double Arming enters, put a +1/+1 counter on enchanted creature.
Enchanted creature has menace.
{5}: Return Double Arming to its owner's hand.

First strike, haste
Whenever you cast a spell, Double-Edged Duelist gains double strike until end of turn if that spell has the same name as a card in your graveyard.

Return target nonland permanent you control and target nonland permanent you don't control to their owners' hands.
{2}{U}, Exile Doubt Oneself from your graveyard: Search your library for a card named Study Oneself, reveal it, put it into your hand, then shuffle.

Other creatures you control get +1/+1.
Lands you control enter tapped.

Double strike, trample
Enchantment spells you cast cost {1} less to cast.
Whenever you put a lore counter on a Saga you control, Douglass, Star of the Show gets +1/+1 until end of turn.

Douse in Flame deals 5 damage to target creature without flying. When that creature leaves the battlefield this turn, exile its controller's graveyard.

{T}, Sacrifice an Equipment: Return target Equipment card from your graveyard to the battlefield. Activate only as a sorcery.

Primal—Reappropriate green. (During your turn, you may cast this spell by exiling two green cards from your hand and/or graveyard instead of playing a land.)
When Dovon's Masterwork enters, return target land card from your graveyard to the battlefield tapped.

{T}: Add {G}.
{B/G}, {T}: Exile target card from a graveyard. If that card is a creature card, put a +1/+1 counter on Dovon, Verdant Experimenter and you gain 1 life.