Underdome

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

Secret Base

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a spell that shares a watermark with Secret Base.

Evolving Wilds

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Steel Squirrel

Whenever you roll a 5 or higher on a die, Steel Squirrel gets +X/+X until end of turn, where X is the result.
{6}: Roll a six-sided die.

Three-Headed Goblin

Triple strike (This creature deals first-strike, regular, and last-strike combat damage.)

As Luck Would Have It

Hexproof
Whenever you roll a die, put a number of luck counters on As Luck Would Have It equal to the result. Then if there are 100 or more luck counters on As Luck Would Have It, you win the game. (Count both rolls if you reroll a die.)

Garbage Elemental

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
When Garbage Elemental enters, roll a six-sided die. Garbage Elemental deals damage equal to the result to target opponent or planeswalker.

Party Crasher

Haste
You can attack with Party Crasher once each combat during each opponent's turn.

Krazy Kow

At the beginning of your upkeep, roll a six-sided die. If you a roll a 1, sacrifice Krazy Kow and it deals 3 damage to each creature and each player.

Ol' Buzzbark

When Ol' Buzzbark enters, roll X six-sided dice onto the battlefield from a height of at least X inches. For each die, put a number of +1/+1 counters equal to the result on each creature you control that die is touching. For each die, Ol' Buzzbark deals damage equal to the result to each creature an opponent controls that die is touching.

Hammer Jammer

As Hammer Jammer enters, roll a six-sided die. Hammer Jammer enters with a number of +1/+1 counters on it equal to the result.
Whenever you roll a die, remove all +1/+1 counters from Hammer Jammer, then put a number of +1/+1 counters on it equal to the result.

Mountain

Forest

Ground Pounder

{3}{G}: Roll a six-sided die. Ground Pounder gets +X/+X until end of turn, where X is the result.
Whenever you roll a 5 or higher on a die, Ground Pounder gains trample until end of turn.

Kazandu Refuge

Kazandu Refuge enters tapped.
When Kazandu Refuge enters, you gain 1 life.
{T}: Add {R} or {G}.

Chittering Doom

Whenever you roll a 4 or higher on a die, create a 1/1 green Squirrel creature token.

Earl of Squirrel

Squirrellink (Damage dealt by this creature also causes you to create that many 1/1 green Squirrel creature tokens.)
Creature tokens you control are Squirrels in addition to their other creature types.
Other Squirrels you control get +1/+1.

Krark's Other Thumb

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

Lobe Lobber

Equipped creature has "{T}: This creature deals 1 damage to target player or planeswalker. Roll a six-sided die. On a 5 or higher, untap it."
Equip {2}

Ineffable Blessing

As Ineffable Blessing enters, choose odd or even.
Whenever a creature you control with a collector number of the chosen value enters, draw a card.

Box of Free-Range Goblins

Roll a six-sided die. Create a number of 1/1 red Goblin creature tokens equal to the result.

Goblin Bookie

{R}, {T}: Reflip any coin or reroll any die. (Activate only any time it makes sense.)

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.