msem-instigator

Up to one target creature gets -2/-2 until end of turn. Put a +1/+1 counter on up to one target creature you control.

When Undermarket Favors enters the battlefield, target player discards a card, then mills four cards.
{1}, Sacrifice Undermarket Favors: Draw a card.

Flash
If an opponent would draw a card, that player exiles the top card of their library instead. During each player's turn, that player may play that card for as long as it remains exiled.

{T}, Pay 1 life: Add one mana of any color that a land an opponent controls could produce.

Bleed {1}{B} (You may cast this spell for its bleed cost if an opponent lost life this turn.)
When Undermurk Scavenger enters the battlefield, you draw a card and you lose 1 life.

Vigilance
Whenever Underpass Sentinel enters the battlefield or attacks, you may put a +1/+1 counter on another target creature you control without one.
Sacrifice Underpass Sentinel: Embattled creatures you control gain hexproof and indestructible until end of turn. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

As an additional cost to cast this spell, exile a creature card from your graveyard.
You draw three cards and you lose 3 life.

At the beginning of your upkeep, reveal the top card of your library. If it has the same name as a card in your graveyard, put the revealed card into your hand. Otherwise, put it into your graveyard.

Colossal 2—{4}{B} (You may cast this for its colossal cost to have it enter with two +1/+1 counters; or pay {4}{B} as a sorcery: Put two +1/+1 counters on it if it has none.)
Lifelink

Undine Coven gets +1/+1 for each other Merfolk you control.
Whenever you cast a noncreature spell, Undine Coven deals 1 damage to target player or planeswalker.

Archive 0 (As this enters the battlefield, shuffle the top zero cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
As Undue's Study enters the battlefield, shuffle your graveyard into the archived library.

[+2]: Exile up to three target cards from graveyards.
[+1]: Create a 2/1 black Horse Zombie creature token with lifelink.
[0]: If Undue has six or more loyalty counters on him, each opponent returns a creature card of their choice from a graveyard to the battlefield under your control.

Return up to two target creature cards with total mana value 4 or less from your graveyard to the battlefield.

When Undying Lich dies, create a 6/3 black Zombie Horror creature token with menace and “When this creature dies, create an 8/5 black Elder Demon Horror creature token with flying, deathtouch, and menace.”

Zombiecycling {1}{B} ({1}{B}, Discard this card: Search your library for a Zombie card, reveal it, and put it into your hand, then shuffle.)
Unearth {1}{B} ({1}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the end step or if it would leave the battlefield. Unearth only as a sorcery.)

Mill four cards, then return any number of creature cards with total mana value 4 or less from your graveyard to the battlefield.

Creatures you control get +2/+0 and have deathtouch as long as ten or more cards are in your graveyard.

When Undying Watcher enters the battlefield, germinate. (Put a +1/+1 counter on a creature or create a 1/1 green Saproling creature token.)
Sacrifice another creature: Undying Watcher gains indestructible until end of turn.

Create a 2/2 black Zombie creature token, then sacrifice a creature.

Return target creature card with mana value 3 or less from your graveyard to the battlefield.
Cycling {2} ({2}, Discard this card: Draw a card.)

Return up to two target creature cards from your graveyard to your hand. You lose 2 life.

Unearthed Legion's power and toughness are each equal to the number of cards in your graveyard.
At the beginning of your upkeep, mill a card.

Whenever a creature you control dies, you may return all cards that were inscribed onto that creature and all Auras that were attached to that creature to their owners' hands.

Create three 1/1 colorless Servo artifact creature tokens.
Exile Unending Armies. At the beginning of your upkeep, if you have more life than each opponent, you may cast it without paying its mana cost. Otherwise, put it into your graveyard.

Unending Slime enters the battlefield with X +1/+1 counters on it.
{2}{G}{G}{G}: Return Unending Slime from your graveyard to your hand.