Chaos Wrap

The owner of target permanent shuffles it into their library. Then they may look at the top card of their library and may wrap it. If it's a permanent card, they may put it onto the battlefield. Otherwise, they may put it onto the battlefield face down as a 4/4 red Present creature. (To wrap a card, put it inside lots of sleeves. If it would be dealt damage or destroyed, remove a sleeve from it instead.)

Zzzyxas's Abyss

At the beginning of your upkeep, destroy all nonland permanents with the first name alphabetically among nonland permanents.

Censorship

As Censorship enters, choose a word.
Whenever a player says the chosen word, Censorship deals 2 damage to that player.

Name Dropping

Gotcha — If an opponent says a word that's in the name of a card in your graveyard, you may say "Gotcha!" When you do, return that card to your hand.

Mox Lotus

{T}: Add {∞}.
{100}: Add one mana of any color.

Last-Minute Chopping

Ask target opponent if they remembered to get you a present. If they say yes, they put a card they own from outside the game into your hand. Otherwise, you gain control of target permanent they control.

Aven Mindcensor

Flash
Flying
If an opponent would search a library, that player searches the top four cards of that library instead.

World-Bottling Kit

{5}, Sacrifice World-Bottling Kit: Choose a Magic set. Exile all permanents with that set's expansion symbol except for basic lands.

Snow Mercy

Whenever a creature deals damage to you, put a globe counter on it.
{T}, {Q}, {T}, {Q}, {T}: Tap all creatures with globe counters on them.

Look at Me, I'm the DCI

Ban a card other than a basic land card for the rest of the match. (All cards with that name in any zone or sideboard are removed from the match.)

Seasonal Sequels

Pitch the titles of up to X holiday-themed sequels to target spell. Copy that spell for each title pitched, except the copy has that name. You may choose new targets for the copies. (Simply adding numbers isn't festive enough.)

Bog Humbugs

Flying
Whenever Bog Humbugs deals combat damage, hum that many notes of a festive song. If you can, put a +1/+1 counter on Bog Humbugs.

Eggnogger's 'Stache

Lands you control have "{T}: Refill your mug with a festive drink." (If you don't have a mug, go grab a mug! It's the holidays!)
At the beginning of combat on your turn, if you have a drink 'stache, put two +1/+1 counters on each creature you control.

Booster Tutor

Open a sealed Magic booster pack, reveal the cards, and put one of them into your hand. (Remove that card from your deck before beginning a new game.)

Fruitcake Elemental

Fruitcake Elemental is indestructible.
At the end of your turn, Fruitcake Elemental deals 7 damage to you.
{3}: Target player gains control of Fruitcake Elemental.

Goblin Sleigh Ride

Target creature you control climbs into Goblin Sleigh Ride. You slide them on their merry way. If the creature stayed on, it deals damage equal to its toughness to each other creature touched during the slide.

Super Secret Tech

Premium spells cost {1} less to cast.
Premium creatures get +1/+1.

Vorthos, Steward of Myth

As Vorthos, Steward of Myth enters, choose a named Magic character.
Each spell you cast with the chosen character in its name, flavor text, or art costs {W}{U}{B}{R}{G} less to cast. This effect reduces only the amount of colored mana you pay.

Gifts Given

Search target opponent's library for four cards with different names and reveal them. That player chooses two of those cards. Put the chosen cards into the player's graveyard and the rest into your hand. Then that player shuffles their library.

Head to Head

You and target opponent play Seven Questions with the top card of that player's library. If you win, prevent all damage that would be dealt this turn by a source of your choice. (To play Seven Questions, that player looks at the card, then you ask up to six yes-or-no questions about the card that they answer truthfully. You guess the card's name—that's question seven—then the player reveals the card.)

Flaccify

Counter target spell unless its controller pays {3}{½}.

Thopter Pie Network

At the beginning of your upkeep, if you're eating, create a 1/1 colorless Thopter artifact creature token with flying. Use food to represent the token.
Whenever a creature token you control dies, if it's represented by food, eat it.

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.

Avatar of Me

This spell costs {1} more to cast for each ten years you've been alive.
Avatar of Me's power is equal to your height in feet and its toughness is equal to your American shoe size. Round to the nearest ½.
Avatar of Me is the color of your eyes.

Present Arms

Exchange your library with another deck you own from outside the game. Shuffle your library.

Decorated Knight

Whenever Decorated Knight attacks, draw a card from your original deck if it's outside the game.

Decorated Knight // Present Arms

Jalum Grifter

{1}{R}, {T}: Shuffle Jalum Grifter and two lands you control face down. Target opponent chooses one of those cards. Turn the cards face up. If they chose Jalum Grifter, sacrifice it. Otherwise, destroy target permanent.

Season's Beatings

Family gathering — Each creature target player controls deals damage equal to its power to another random creature that player controls.

Incoming!

Each player searches their library for any number of artifact, creature, enchantment, and/or land cards, puts them onto the battlefield, then shuffles.

Some Disassembly Required

{B}, Sacrifice a creature: Distribute the sacrificed creature's keyword abilities among any number of other target creatures until end of turn. If it's December, you gain 1 life for each of those keywords.

Richard Garfield, Ph.D.

You may play cards as though they were other cards of your choice with the same mana cost. You can't choose the same card twice. (Mana cost includes color.)

Evil Presents

Put a creature card from your hand into play under target opponent's control. That creature attacks each turn if able . . . and always attacks its controller.

R&D's Secret Lair

Play cards as written. Ignore all errata.
{T}: Add {C}. (This mana is still added to your mana pool.)

Nice

Search your library for a card and put it into another target player's hand. Then shuffle your library.

Naughty

Search another target player's library for a card and put that card into your hand. Then shuffle that player's library.

Naughty // Nice

Checks and Balances

Cast this spell only if there are three or more players in the game.
Whenever a player casts a spell, each of that player's opponents may discard a card. If they do, counter that spell.

Mine, Mine, Mine!

When Mine, Mine, Mine! enters, each player puts their library into their hand.
Players have no maximum hand size and don't lose the game for drawing from an empty library.
Each player can't cast more than one spell each turn.
When Mine, Mine, Mine! leaves the battlefield, each player shuffles their hand and graveyard into their library.

Mise

Choose a nonland card name, then reveal the top card of your library. If that card has the chosen name, you draw three cards.

Yule Ooze

At the beginning of your upkeep, destroy another nonland permanent chosen at random, then put a number of +1/+1 counters on Yule Ooze equal to that permanent's converted mana cost.
{R}{G}, Eat some food: Regenerate Yule Ooze.

Topdeck the Halls

Decorated cards in your hand have miracle {S}. (Decorated cards include premiums, promos, and cards with alternate frames or art.)
At the beginning of your upkeep, if you control twelve or more decorated permanents, you win the game.

Stocking Tiger

Stocking Tiger enters with a sealed Magic booster pack under it.
When Stocking Tiger deals combat damage to a player, unwrap the booster pack and put it into your hand.

Omniscience

You may cast spells from your hand without paying their mana costs.

Fowl Play

Enchant creature
Enchanted creature loses all abilities and is a Bird creature with base power and toughness 1/1.