Saiba Cryptomancer

Flash
Backup 1 (When this creature enters, put a +1/+1 counter on target creature. If that's another creature, it gains the following ability until end of turn.)
Hexproof

Dimir Keyrune

{T}: Add {U} or {B}.
{U}{B}: Dimir Keyrune becomes a 2/2 blue and black Horror artifact creature until end of turn and can't be blocked this turn.

Vivisurgeon's Insight

Draw three cards. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Have

Jon Irenicus, Shattered One

At the beginning of your end step, target opponent gains control of up to one target creature you control. Put two +1/+1 counters on it and tap it. It's goaded for the rest of the game and it gains "This creature can't be sacrificed." (It attacks each combat if able and attacks a player other than you if able.)
Whenever a creature you own but don't control attacks, you draw a card.

Fettergeist

Flying
At the beginning of your upkeep, sacrifice Fettergeist unless you pay {1} for each other creature you control.

Persist

Return target nonlegendary creature card from your graveyard to the battlefield with a -1/-1 counter on it.

Archfiend of the Dross

Flying
Archfiend of the Dross enters with four oil counters on it.
At the beginning of your upkeep, remove an oil counter from Archfiend of the Dross. Then if it has no oil counters on it, you lose the game.
Whenever a creature an opponent controls dies, its controller loses 2 life.

Vat Emergence

Put target creature card from a graveyard onto the battlefield under your control. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Blood Pet

Bind the Monster

Enchant creature
When Bind the Monster enters, tap enchanted creature. It deals damage to you equal to its power.
Enchanted creature doesn't untap during its controller's untap step.

Ulamog's Crusher

Annihilator 2 (Whenever this creature attacks, defending player sacrifices two permanents of their choice.)
Ulamog's Crusher attacks each combat if able.

Done

Tap up to two target creatures. Those creatures don't untap during their controller's next untap step.

Said

Return target instant or sorcery card from your graveyard to your hand.

Said // Done

Wretched Anurid

Whenever another creature enters, you lose 1 life.

Geth, Thane of Contracts

Other creatures you control get -1/-1.
{1}{B}{B}, {T}: Return target creature card from your graveyard to the battlefield. It gains "If this creature would leave the battlefield, exile it instead of putting it anywhere else." Activate only as a sorcery.

Modify Memory

Exchange control of two target creatures controlled by different players. If you control neither creature, draw three cards.

Flesh Reaver

Whenever Flesh Reaver deals damage to a creature or opponent, Flesh Reaver deals that much damage to you.

Forsaken Drifters

When Forsaken Drifters dies, mill four cards.

Paralyzing Grasp

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.

Switcheroo

Exchange control of two target creatures.

Recoil

Return target permanent to its owner's hand. Then that player discards a card.

Dimir Cluestone

{T}: Add {U} or {B}.
{U}{B}, {T}, Sacrifice Dimir Cluestone: Draw a card.

Nezumi Informant

When Nezumi Informant enters, each opponent discards a card.

Gitaxian Mindstinger

Deathtouch
Whenever Gitaxian Mindstinger deals combat damage to a player or battle, draw a card.

Aetherblade Agent

Deathtouch
{4}{U/P}: Transform Aetherblade Agent. Activate only as a sorcery. ({U/P} can be paid with either {U} or 2 life.)

Aetherblade Agent // Gitaxian Mindstinger

Incriminate

Choose two target creatures controlled by the same player. That player sacrifices one of them of their choice.

The Surgical Bay

The Surgical Bay enters tapped.
{T}: Add {U}.
{1}{U}, {T}, Sacrifice The Surgical Bay: Draw a card.

Contaminated Aquifer

({T}: Add {U} or {B}.)
Contaminated Aquifer enters tapped.

The Dross Pits

The Dross Pits enters tapped.
{T}: Add {B}.
{1}{B}, {T}, Sacrifice The Dross Pits: Draw a card.

Accursed Spirit

Intimidate (This creature can't be blocked except by artifact creatures and/or creatures that share a color with it.)