Painiac

At the beginning of your upkeep, roll a six-sided die. Painiac gets +X/+0 until end of turn, where X is the result.

Underdome

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to pay Un-costs.

Krark's Other Thumb

If you would roll a die, instead roll two of those dice and ignore one of those results.

Goblin Haberdasher

Menace (This creature can't be blocked except by two or more creatures.)
Other creatures you control wearing hats in their art have menace.

Ayara, First of Locthwain

Whenever Ayara, First of Locthwain or another black creature you control enters, each opponent loses 1 life and you gain 1 life.
{T}, Sacrifice another black creature: Draw a card.

Hoisted Hireling

Hoisted Hireling has flying as long as it's being held above the battlefield.

Infinity Elemental

Snickering Squirrel

You may tap Snickering Squirrel to increase the result of a die any player rolled by 1.

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.)

Mox Lotus

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

Skull Saucer

Flying
When Skull Saucer enters, destroy target creature and put your head on the table. Sacrifice Skull Saucer when your head stops touching the table.

Discord, Lord of Disharmony

Flying
At the beginning of your end step, choose a random nonland Magic card name. Until your next end step, you may cast a copy of a spell with that name, and mana of any type can be spent to cast it. If you cast a spell this way, copy this ability if Discord is on the battlefield.

Swamp

Poultrygeist

Flying
Whenever a creature dies, you may roll a six-sided die. If you roll a 1, sacrifice Poultrygeist. Otherwise, put a +1/+1 counter on Poultrygeist.

Destroy target creature with reminder text. (Reminder text is any italicized text in parentheses that explains rules you already know.)

Goblin S.W.A.T. Team

Say "Goblin S.W.A.T. Team": Put a +1/+1 counter on Goblin S.W.A.T. Team unless an opponent swats the table within five seconds. Activate only once each turn.

Pointy Finger of Doom

{3}, {T}: Spin Pointy Finger of Doom in the middle of the table so that it rotates completely at least once, then destroy the closest permanent the finger points to.

Inhumaniac

At the beginning of your upkeep, roll a six-sided die. On a 3 or 4, put a +1/+1 counter on Inhumaniac. On a 5 or higher, put two +1/+1 counters on it. On a 1, remove all +1/+1 counters from Inhumaniac.

Enter the Dungeon

Players play a Magic subgame under the table, starting at 5 life and using their libraries as their decks. The winner searches their library for two cards, puts those cards into their hand, then shuffles.

Six-y Beast

As Six-y Beast enters, you secretly put six or fewer +1/+1 counters on it, then an opponent guesses the number of counters. If that player guesses right, sacrifice Six-y Beast after it enters.

Yet Another Aether Vortex

All creatures have haste.
Players play with the top card of their libraries revealed.
Noninstant, nonsorcery cards on top of a library are on the battlefield under their owner's control in addition to being in that library.

Mountain

Boomstacker

As Boomstacker enters and whenever it attacks, stack two dice on top of it. (All dice must be stacked vertically, one on top of another.)
Boomstacker gets +1/+1 for each die in its stack.
Boomstacker attacks each combat if able.
When the stack falls, sacrifice Boomstacker.

Jumbo Imp

Flying
As Jumbo Imp enters, roll a six-sided die. Jumbo Imp enters with a number of +1/+1 counters on it equal to the result.
At the beginning of your upkeep, roll a six-sided die and put a number of +1/+1 counters on Jumbo Imp equal to the result.
At the beginning of your end step, roll a six-sided die and remove a number of +1/+1 counters from Jumbo Imp equal to the result.