Ensnared by the Mara

Each opponent faces a villainous choice — They exile cards from the top of their library until they exile a nonland card, then you may cast that card without paying its mana cost, or that player exiles the top four cards of their library and Ensnared by the Mara deals damage equal to the total mana value of those exiled cards to that player.

Prisoner's Dilemma

Each opponent secretly chooses silence or snitch, then the choices are revealed. If each opponent chose silence, Prisoner's Dilemma deals 4 damage to each of them. If each opponent chose snitch, Prisoner's Dilemma deals 8 damage to each of them. Otherwise, Prisoner's Dilemma deals 12 damage to each opponent who chose silence.
Flashback {5}{R}{R}

Blood Crypt

({T}: Add {B} or {R}.)
As Blood Crypt enters, you may pay 2 life. If you don't, it enters tapped.

Exotic Orchard

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

Fabricate

Search your library for an artifact card, reveal it, put it into your hand, then shuffle.

Ancient Copper Dragon

Flying
Whenever Ancient Copper Dragon deals combat damage to a player, roll a d20. You create a number of Treasure tokens equal to the result.

Sygg, River Cutthroat

At the beginning of each end step, if an opponent lost 3 or more life this turn, you may draw a card. (Damage causes loss of life.)

Dragon's Approach

Dragon's Approach deals 3 damage to each opponent. You may exile Dragon's Approach and four cards named Dragon's Approach from your graveyard. If you do, search your library for a Dragon creature card, put it onto the battlefield, then shuffle.
A deck can have any number of cards named Dragon's Approach.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Nightscape Familiar

Blue spells and red spells you cast cost {1} less to cast.
{1}{B}: Regenerate Nightscape Familiar.

Swamp

Auton Soldier

You may have Auton Soldier enter as a copy of any creature on the battlefield, except it isn't legendary, is an artifact in addition to its other types, and has myriad. (Whenever it attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

Dalek Drone

Flying, menace
Exterminate! — When Dalek Drone enters, destroy target creature an opponent controls. That player loses 3 life.

Rakdos Signet

Cyclonic Rift

Return target nonland permanent you don't control to its owner's hand.
Overload {6}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Davros, Dalek Creator

Menace
At the beginning of your end step, create a 3/3 black Dalek artifact creature token with menace if an opponent lost 3 or more life this turn. Then each opponent who lost 3 or more life this turn faces a villainous choice — You draw a card, or that player discards a card.

Goldspan Dragon

Flying, haste
Whenever Goldspan Dragon attacks or becomes the target of a spell, create a Treasure token.
Treasures you control have "{T}, Sacrifice this artifact: Add two mana of any one color."

Steam Vents

({T}: Add {U} or {R}.)
As Steam Vents enters, you may pay 2 life. If you don't, it enters tapped.

Cyber Conversion

Turn target creature face down. It's a 2/2 Cyberman artifact creature.

Pyromancer Ascension

Whenever you cast an instant or sorcery spell that has the same name as a card in your graveyard, you may put a quest counter on Pyromancer Ascension.
Whenever you cast an instant or sorcery spell while Pyromancer Ascension has two or more quest counters on it, you may copy that spell. You may choose new targets for the copy.

Cyberman Patrol

Artifact creatures you control have afflict 3. (Whenever a creature with afflict 3 becomes blocked, defending player loses 3 life.)

The Dalek Emperor

Affinity for Daleks (This spell costs {1} less to cast for each Dalek you control.)
Other Daleks you control have haste.
At the beginning of combat on your turn, each opponent faces a villainous choice — That player sacrifices a creature of their choice, or you create a 3/3 black Dalek artifact creature token with menace.

Locket of Yesterdays

Spells you cast cost {1} less to cast for each card with the same name as that spell in your graveyard.

Bonehoard Dracosaur

Flying, first strike
At the beginning of your upkeep, exile the top two cards of your library. You may play them this turn. If you exiled a land card this way, create a 3/1 red Dinosaur creature token. If you exiled a nonland card this way, create a Treasure token.

Smoldering Marsh

({T}: Add {B} or {R}.)
Smoldering Marsh enters tapped unless you control two or more basic lands.

Thrumming Stone

Spells you cast have ripple 4. (Whenever you cast a spell, you may reveal the top four cards of your library. You may cast spells with the same name as that spell from among the revealed cards without paying their mana costs. Put the rest on the bottom of your library.)

Loyal Subordinate

Menace (This creature can't be blocked except by two or more creatures.)
Lieutenant — At the beginning of combat on your turn, if you control your commander, each opponent loses 3 life.

Bloodletter of Aclazotz

Flying
If an opponent would lose life during your turn, they lose twice that much life instead. (Damage causes loss of life.)

Sol Ring

Goblin Electromancer

Instant and sorcery spells you cast cost {1} less to cast.

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Mountain

Dragonskull Summit

Dragonskull Summit enters tapped unless you control a Swamp or a Mountain.
{T}: Add {B} or {R}.

Island

Hoarding Dragon

Flying
When Hoarding Dragon enters, you may search your library for an artifact card, exile it, then shuffle.
When Hoarding Dragon dies, you may put the exiled card into its owner's hand.

Drakuseth, Maw of Flames

Flying
Whenever Drakuseth, Maw of Flames attacks, it deals 4 damage to any target and 3 damage to each of up to two other targets.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Thought Vessel

Haunted Ridge

Haunted Ridge enters tapped unless you control two or more other lands.
{T}: Add {B} or {R}.

Arcane Signet

Wound Reflection

At the beginning of each end step, each opponent loses life equal to the life they lost this turn. (Damage causes loss of life.)

Arcum Dagsson

{T}: Target artifact creature's controller sacrifices it. That player may search their library for a noncreature artifact card, put it onto the battlefield, then shuffle.

Terror of the Peaks

Flying
Spells your opponents cast that target Terror of the Peaks cost an additional 3 life to cast.
Whenever another creature you control enters, Terror of the Peaks deals damage equal to that creature's power to any target.

Talisman of Creativity

{T}: Add {C}.
{T}: Add {U} or {R}. Talisman of Creativity deals 1 damage to you.

The Valeyard

If an opponent would face a villainous choice, they face that choice an additional time. (They can make the same or different choices.)
While voting, you may vote an additional time.

Exterminate!

Replicate—Tap an untapped Dalek you control. (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)
Destroy target creature. Its controller loses 3 life.

Stormcarved Coast

Stormcarved Coast enters tapped unless you control two or more other lands.
{T}: Add {U} or {R}.

Reshape

As an additional cost to cast this spell, sacrifice an artifact.
Search your library for an artifact card with mana value X or less, put it onto the battlefield, then shuffle.