Obeka, Splitter of Seconds

Menace
Whenever Obeka, Splitter of Seconds deals combat damage to a player, you get that many additional upkeep steps after this phase.

Exalted Flamer of Tzeentch

Sorcerous Inspiration — At the beginning of your upkeep, return an instant or sorcery card at random from your graveyard to your hand.
Fire of Tzeentch — Whenever you cast an instant or sorcery spell, Exalted Flamer of Tzeentch deals 1 damage to each opponent.

The Tenth Doctor

Allons-y! — Whenever you attack, exile cards from the top of your library until you exile a nonland card. Put three time counters on it. If it doesn't have suspend, it gains suspend.
Timey-Wimey — {7}: Time travel three times. Activate only as a sorcery. (For each suspended card you own and each permanent you control with a time counter on it, you may add or remove a time counter. Then do it two more times.)

Snap

Return target creature to its owner's hand. Untap up to two lands.

Arcane Signet

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

Withering Torment

Destroy target creature or enchantment. You lose 2 life.

As Foretold

At the beginning of your upkeep, put a time counter on As Foretold.
Once each turn, you may pay {0} rather than pay the mana cost for a spell you cast with mana value X or less, where X is the number of time counters on As Foretold.

Relic of Legends

{T}: Add one mana of any color.
Tap an untapped legendary creature you control: Add one mana of any color.

Xander's Lounge

({T}: Add {U}, {B}, or {R}.)
Xander's Lounge enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Sulfur Falls

Sulfur Falls enters tapped unless you control an Island or a Mountain.
{T}: Add {U} or {R}.

Creeping Bloodsucker

At the beginning of your upkeep, Creeping Bloodsucker deals 1 damage to each opponent. You gain life equal to the damage dealt this way.

Clara Oswald

Impossible Girl — If Clara Oswald is your commander, choose a color before the game begins. Clara Oswald is the chosen color.
If a triggered ability of a Doctor you control triggers, that ability triggers an additional time.
Doctor's companion (You can have two commanders if the other is the Doctor.)

Xanathar, Guild Kingpin

At the beginning of your upkeep, choose target opponent. Until end of turn, that player can't cast spells, you may look at the top card of their library any time, you may play the top card of their library, and you may spend mana as though it were mana of any color to cast spells this way.

Sakashima of a Thousand Faces

You may have Sakashima of a Thousand Faces enter as a copy of another creature you control, except it has Sakashima of a Thousand Faces's other abilities.
The "legend rule" doesn't apply to permanents you control.
Partner (You can have two commanders if both have partner.)

Tamiyo's Journal

At the beginning of your upkeep, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
{T}, Sacrifice three Clues: Search your library for a card, put that card into your hand, then shuffle.

Twilight Prophet

Flying
Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
At the beginning of your upkeep, if you have the city's blessing, reveal the top card of your library and put it into your hand. Each opponent loses X life and you gain X life, where X is that card's mana value.

Kumena's Awakening

Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
At the beginning of your upkeep, each player draws a card. If you have the city's blessing, instead only you draw a card.

Mirrormade

You may have Mirrormade enter as a copy of any artifact or enchantment on the battlefield.

Replicating Ring

{T}: Add one mana of any color.
At the beginning of your upkeep, put a night counter on Replicating Ring. Then if it has eight or more night counters on it, remove all of them and create eight colorless snow artifact tokens named Replicated Ring with "{T}: Add one mana of any color."

Crumbling Necropolis

Crumbling Necropolis enters tapped.
{T}: Add {U}, {B}, or {R}.

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

Tempting Contract

At the beginning of your upkeep, each opponent may create a Treasure token. For each opponent who does, you create a Treasure token.

Quantum Misalignment

Create a token that's a copy of target creature you control, except it isn't legendary.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Watery Grave

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

Court of Embereth

When Court of Embereth enters, you become the monarch.
At the beginning of your upkeep, create a 3/1 red Knight creature token. Then if you're the monarch, Court of Embereth deals X damage to each opponent, where X is the number of creatures you control.

Court of Locthwain

When Court of Locthwain enters, you become the monarch.
At the beginning of your upkeep, exile the top card of target opponent's library. You may play that card for as long as it remains exiled, and mana of any type can be spent to cast it. If you're the monarch, until end of turn, you may cast a spell from among cards exiled with Court of Locthwain without paying its mana cost.

Shipwreck Marsh

Shipwreck Marsh enters tapped unless you control two or more other lands.
{T}: Add {U} or {B}.

Command Tower

Dragonmaster Outcast

At the beginning of your upkeep, if you control six or more lands, create a 5/5 red Dragon creature token with flying.

Steam Vents

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

Blood Crypt

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

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.

TARDIS

Flying
Whenever TARDIS attacks, if you control a Time Lord, the next spell you cast this turn has cascade and you may planeswalk.
Crew 2 (Tap any number of creatures you control with total power 2 or more: This Vehicle becomes an artifact creature until end of turn.)

Star Whale

Flying, vigilance
Other creatures you control have ward {2}.
Suspend 6—{1}{U} (Rather than cast this card from your hand, you may pay {1}{U} and exile it with six time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Sphinx of the Second Sun

Flying
At the beginning of each of your postcombat main phases, there is an additional beginning phase after this phase. (The beginning phase includes the untap, upkeep, and draw steps.)

Dominus of Fealty

Flying
At the beginning of your upkeep, you may gain control of target permanent until end of turn. If you do, untap it and it gains haste until end of turn.

Honden of Seeing Winds

At the beginning of your upkeep, draw a card for each Shrine you control.

Shadow of the Second Sun

Enchant player
At the beginning of each of enchanted player's postcombat main phases, there is an additional beginning phase after this phase. (The end step happens after the added untap, upkeep, and draw steps.)

Island

Magmatic Force

At the beginning of each upkeep, Magmatic Force deals 3 damage to any target.

Mountain

Stormcarved Coast

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

Jhoira of the Ghitu

{2}, Exile a nonland card from your hand: Put four time counters on the exiled card. If it doesn't have suspend, it gains suspend. (At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. If it's a creature, it has haste.)

Court of Ire

When Court of Ire enters, you become the monarch.
At the beginning of your upkeep, Court of Ire deals 2 damage to any target. If you're the monarch, it deals 7 damage instead.

Mox Tantalite

Suspend 3—{0} (Rather than cast this card from your hand, pay {0} and exile it with three time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)
{T}: Add one mana of any color.

Counterspell

Skyline Despot

Flying
When Skyline Despot enters, you become the monarch.
At the beginning of your upkeep, if you're the monarch, create a 5/5 red Dragon creature token with flying.

Patient Rebuilding

At the beginning of your upkeep, target opponent mills three cards, then you draw a card for each land card put into their graveyard this way.

Infernal Grasp

Destroy target creature. You lose 2 life.

Reliquary Tower

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

Thopter Spy Network

At the beginning of your upkeep, if you control an artifact, create a 1/1 colorless Thopter artifact creature token with flying.
Whenever one or more artifact creatures you control deal combat damage to a player, draw a card.

Court of Ambition

When Court of Ambition enters, you become the monarch.
At the beginning of your upkeep, each opponent loses 3 life unless they discard a card. If you're the monarch, instead each opponent loses 6 life unless they discard two cards.

Thought Vessel

Venser's Journal

You have no maximum hand size.
At the beginning of your upkeep, you gain 1 life for each card in your hand.

Wildfire Devils

When Wildfire Devils enters and at the beginning of your upkeep, choose a player at random. That player exiles an instant or sorcery card from their graveyard. Copy that card. You may cast the copy without paying its mana cost.

Collective Nightmare

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Target creature gets -3/-3 until end of turn.

Roaming Throne

Ward {2}
As Roaming Throne enters, choose a creature type.
Roaming Throne is the chosen type in addition to its other types.
If a triggered ability of another creature you control of the chosen type triggers, it triggers an additional time.

Deadly Rollick

If you control a commander, you may cast this spell without paying its mana cost.
Exile target creature.

Luxury Suite

Luxury Suite enters tapped unless you have two or more opponents.
{T}: Add {B} or {R}.

Sol Ring

Vandalblast

Destroy target artifact you don't control.
Overload {4}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Training Center

Training Center enters tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Court of Vantress

When Court of Vantress enters, you become the monarch.
At the beginning of your upkeep, choose up to one other target enchantment or artifact. If you're the monarch, you may create a token that's a copy of it. If you're not the monarch, you may have Court of Vantress become a copy of it, except it has this ability.

Deflecting Swat

If you control a commander, you may cast this spell without paying its mana cost.
You may choose new targets for target spell or ability.

Paradise Mantle

Equipped creature has "{T}: Add one mana of any color."
Equip {1}

Chaos Warp

The owner of target permanent shuffles it into their library, then reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

Indulgent Tormentor

Flying
At the beginning of your upkeep, draw a card unless target opponent sacrifices a creature of their choice or pays 3 life.

Unable to Scream

Enchant creature
Enchanted creature loses all abilities and is a Toy artifact creature with base power and toughness 0/2 in addition to its other types.
As long as enchanted creature is face down, it can't be turned face up.

Paradox Haze

Enchant player
At the beginning of enchanted player's first upkeep each turn, that player gets an additional upkeep step after this step.

Aetherize

Return all attacking creatures to their owner's hand.

Sin Prodder

Menace
At the beginning of your upkeep, reveal the top card of your library. Any opponent may have you put that card into your graveyard. If a player does, Sin Prodder deals damage to that player equal to that card's mana value. Otherwise, put that card into your hand.

Court of Cunning

When Court of Cunning enters, you become the monarch.
At the beginning of your upkeep, any number of target players each mill two cards. If you're the monarch, each of those players mills ten cards instead. (To mill a card, a player puts the top card of their library into their graveyard.)

Reverse the Polarity

Choose one —
• Counter all other spells.
• Switch each creature's power and toughness until end of turn.
• Creatures can't be blocked this turn.

Honden of Infinite Rage

At the beginning of your upkeep, Honden of Infinite Rage deals damage to any target equal to the number of Shrines you control.

The Ninth Doctor

Haste
Into the TARDIS — Whenever The Ninth Doctor becomes untapped during your untap step, you get an additional upkeep step after this step.

Swamp

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

Decanter of Endless Water

You have no maximum hand size.
{T}: Add one mana of any color.

Extravagant Replication

At the beginning of your upkeep, create a token that's a copy of another target nonland permanent you control.