Razortrap Gorge

Razortrap Gorge enters tapped unless a player has 13 or less life.
{T}: Add {B} or {R}.

Chant of the Skifsang

Enchant creature
Enchanted creature gets -13/-0.

Sorin the Mirthless

+1: Look at the top card of your library. You may reveal that card and put it into your hand. If you do, you lose life equal to its mana value.
−2: Create a 2/3 black Vampire creature token with flying and lifelink.
−7: Sorin the Mirthless deals 13 damage to any target. You gain 13 life.

Peculiar Lighthouse

Peculiar Lighthouse enters tapped unless a player has 13 or less life.
{T}: Add {U} or {R}.

Emrakul, the Promised End

This spell costs {1} less to cast for each card type among cards in your graveyard.
When you cast this spell, you gain control of target opponent during that player's next turn. After that turn, that player takes an extra turn.
Flying, trample, protection from instants

Triskaidekaphobia

At the beginning of your upkeep, choose one —
• Each player with exactly 13 life loses the game, then each player gains 1 life.
• Each player with exactly 13 life loses the game, then each player loses 1 life.

Into the Maw of Hell

Destroy target land. Into the Maw of Hell deals 13 damage to target creature.

Blasphemous Edict

You may pay {B} rather than pay this spell's mana cost if there are thirteen or more creatures on the battlefield.
Each player sacrifices thirteen creatures of their choice.

Shadow of Mortality

If your life total is less than your starting life total, this spell costs {X} less to cast, where X is the difference.

Bleed Dry

Target creature gets -13/-13 until end of turn. If that creature would die this turn, exile it instead.

Olivia's Midnight Ambush

Target creature gets -2/-2 until end of turn. If it's night, that creature gets -13/-13 until end of turn instead.

Archive Trap

If an opponent searched their library this turn, you may pay {0} rather than pay this spell's mana cost.
Target opponent mills thirteen cards.

Withengar Unbound

Flying, intimidate, trample (A creature with intimidate can't be blocked except by artifact creatures and/or creatures that share a color with it.)
Whenever a player loses the game, put thirteen +1/+1 counters on Withengar Unbound.

Elbrus, the Binding Blade

Equipped creature gets +1/+0.
When equipped creature deals combat damage to a player, unattach Elbrus, the Binding Blade, then transform it.
Equip {1}

Elbrus, the Binding Blade // Withengar Unbound

Persistent Nightmare

Skulk (This creature can't be blocked by creatures with greater power.)
When Persistent Nightmare deals combat damage to a player, return it to its owner's hand.

Startled Awake

Target opponent mills thirteen cards.
{3}{U}{U}: Put Startled Awake from your graveyard onto the battlefield transformed. Activate only as a sorcery.

Startled Awake // Persistent Nightmare

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Tragic Banshee

Morbid — When this creature enters, target creature an opponent controls gets -1/-1 until end of turn. If a creature died this turn, that creature gets -13/-13 instead.

Stensia Uprising

At the beginning of your end step, create a 1/1 red Human creature token. Then if you control exactly thirteen permanents, you may sacrifice Stensia Uprising. When you do, it deals 7 damage to any target.

Army of the Damned

Create thirteen tapped 2/2 black Zombie creature tokens.
Flashback {7}{B}{B}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Triskaidekaphile

You have no maximum hand size.
At the beginning of your upkeep, if you have exactly thirteen cards in your hand, you win the game.
{3}{U}: Draw a card.

Dance with Calamity

Shuffle your library. As many times as you choose, you may exile the top card of your library. If the total mana value of the cards exiled this way is 13 or less, you may cast any number of spells from among those cards without paying their mana costs.

Tragic Fall

Target creature gets -3/-3 until end of turn.
Hellbent — That creature gets -13/-13 until end of turn instead if you have no cards in hand.

Murky Sewer

Murky Sewer enters tapped unless a player has 13 or less life.
{T}: Add {U} or {B}.

Ormendahl, the Corrupter

Flying, trample, lifelink
Sacrifice another creature: Draw a card.

Jerren, Corrupted Bishop

Whenever Jerren, Corrupted Bishop enters or another nontoken Human you control dies, you lose 1 life and create a 1/1 white Human creature token.
{2}: Target Human you control gains lifelink until end of turn.
At the beginning of your end step, if you have exactly 13 life, you may pay {4}{B}{B}. If you do, transform Jerren.

Jerren, Corrupted Bishop // Ormendahl, the Corrupter

Disciple of Perdition

When Disciple of Perdition dies, choose one. If you have exactly 13 life, you may choose both instead.
• You draw a card and you lose 1 life.
• Exile target opponent's graveyard. That player loses 1 life.

Tragic Slip

Target creature gets -1/-1 until end of turn.
Morbid — That creature gets -13/-13 until end of turn instead if a creature died this turn.

Glass-Cast Heart

Whenever one or more Vampires you control attack, create a Blood token. (It's an artifact with "{1}, {T}, Discard a card, Sacrifice this artifact: Draw a card.")
{B}, {T}, Pay 1 life: Create a 1/1 white and black Vampire creature token with lifelink.
{B}{B}, {T}, Sacrifice Glass-Cast Heart and thirteen Blood tokens: Each opponent loses 13 life and you gain 13 life.