Mad Science Fair Project

{T}: Roll a six-sided die. On a 3 or lower, target player adds {C}. Otherwise, that player adds one mana of any color they choose.

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.

Chittering Doom

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

Hydradoodle

As Hydradoodle enters, roll X six-sided dice. Hydradoodle enters with a number of +1/+1 counters on it equal to the total of those results.
Reach, trample

Krark's Other Thumb

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

Forest

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.)

Arcane Investigator

Search the Room — {5}{U}: Roll a d20.
1—9 | Draw a card.
10—20 | Look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order.

Component Pouch

{T}, Remove a component counter from Component Pouch: Add two mana of different colors.
{T}: Roll a d20.
1—9 | Put a component counter on Component Pouch.
10—20 | Put two component counters on Component Pouch.

Sword of Dungeons & Dragons

Equipped creature gets +2/+2 and has protection from Rogues and from Clerics.
Whenever equipped creature deals combat damage to a player, create a 4/4 gold Dragon creature token with flying and roll a d20 (a twenty-sided die). If you roll a 20, repeat this process.
Equip {2}

Mother Kangaroo

When this creature enters, roll a six-sided die. Put a number of +1/+1 counters on this creature equal to the result.

Island

Wall of Fortune

Defender
You may tap an untapped Wall you control to have any player reroll a die that player rolled.

Numbing Jellyfish

When this creature enters, roll a six-sided die. Target player mills X cards, where X is the result.

Willing Test Subject

Reach
Whenever you roll a 4 or higher on a die, put a +1/+1 counter on Willing Test Subject.
{6}: Roll a six-sided die.