Lightfoot Rogue

Sneak Attack — Whenever Lightfoot Rogue attacks, roll a d20.
1—9 | Lightfoot Rogue gains deathtouch until end of turn.
10—19 | It gets +1/+0 and gains deathtouch until end of turn.
20 | It gets +3/+0 and gains first strike and deathtouch until end of turn.

Vexing Puzzlebox

Whenever you roll one or more dice, put a number of charge counters on Vexing Puzzlebox equal to the result.
{T}: Add one mana of any color. Roll a d20.
{T}, Remove 100 charge counters from Vexing Puzzlebox: Search your library for an artifact card, put that card onto the battlefield, then shuffle.

Jan Jansen, Chaos Crafter

Haste
{T}, Sacrifice an artifact creature: Create two Treasure tokens.
{T}, Sacrifice a noncreature artifact: Create two 1/1 colorless Construct artifact creature tokens.

Delina, Wild Mage

Whenever Delina, Wild Mage attacks, choose target creature you control, then roll a d20.
1—14 | Create a tapped and attacking token that's a copy of that creature, except it's not legendary and it has "At end of combat, exile this creature."
15—20 | Create one of those tokens. You may roll again.

Wand of Wonder

{4}, {T}: Roll a d20. Each opponent exiles cards from the top of their library until they exile an instant or sorcery card, then shuffles the rest into their library. You may cast up to X instant and/or sorcery spells from among cards exiled this way without paying their mana costs.
1—9 | X is one.
10—19 | X is two.
20 | X is three.

Mirkwood Bats

Flying
Whenever you create or sacrifice a token, each opponent loses 1 life.

Brazen Dwarf

Whenever you roll one or more dice, Brazen Dwarf deals 1 damage to each opponent.

Myrkul's Edict

Roll a d20.
1—9 | Choose an opponent. That player sacrifices a creature of their choice.
10—19 | Each opponent sacrifices a creature of their choice.
20 | Each opponent sacrifices a creature with the greatest power among creatures that player controls.

Xorn

If you would create one or more Treasure tokens, instead create those tokens plus an additional Treasure token.

Wyll, Blade of Frontiers

If you would roll one or more dice, instead roll that many dice plus one and ignore the lowest roll.
Whenever you roll one or more dice, put a +1/+1 counter on Wyll, Blade of Frontiers.
Choose a Background (You can have a Background as a second commander.)

Mr. House, President and CEO

Whenever you roll a 4 or higher, create a 3/3 colorless Robot artifact creature token. If you rolled 6 or higher, instead create that token and a Treasure token.
{4}, {T}: Roll a six-sided die plus an additional six-sided die for each mana from Treasures spent to activate this ability.

Contraband Livestock

Exile target creature, then roll a d20.
1—9 | Its controller creates a 4/4 green Ox creature token.
10—19 | Its controller creates a 2/2 green Boar creature token.
20 | Its controller creates a 0/1 white Goat creature token.

Hoarding Ogre

Whenever Hoarding Ogre attacks, roll a d20.
1—9 | Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
10—19 | Create two Treasure tokens.
20 | Create three Treasure tokens.

The Deck of Many Things

{2}, {T}: Roll a d20 and subtract the number of cards in your hand. If the result is 0 or less, discard your hand.
1—9 | Return a card at random from your graveyard to your hand.
10—19 | Draw two cards.
20 | Put a creature card from any graveyard onto the battlefield under your control. When that creature dies, its owner loses the game.

Wyll's Reversal

Choose target spell or ability with one or more targets. Roll a d20 and add the greatest power among creatures you control.
1—14 | You may choose new targets for that spell or ability.
15+ | You may choose new targets for that spell or ability. Then copy it. You may choose new targets for the copy.

Comet, Stellar Pup

0: Roll a six-sided die.
1 or 2 — [+2], then create two 1/1 green Squirrel creature tokens. They gain haste until end of turn.
3 — [−1], then return a card with mana value 2 or less from your graveyard to your hand.
4 or 5 — Comet, Stellar Pup deals damage equal to the number of loyalty counters on him to a creature or player, then [−2].
6 — [+1], and you may activate Comet, Stellar Pup's loyalty ability two more times this turn.

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.

Chaos Dragon

Flying, haste
Chaos Dragon attacks each combat if able.
At the beginning of combat on your turn, each player rolls a d20. If one or more opponents had the highest result, Chaos Dragon can't attack those players or planeswalkers they control this combat.

Barbarian Class

(Gain the next level as a sorcery to add its ability.)
If you would roll one or more dice, instead roll that many dice plus one and ignore the lowest roll.
{1}{R}: Level 2
Whenever you roll one or more dice, target creature you control gets +2/+0 and gains menace until end of turn.
{2}{R}: Level 3
Creatures you control have haste.

Academy Manufactor

If you would create a Clue, Food, or Treasure token, instead create one of each.

Alchemist's Talent

(Gain the next level as a sorcery to add its ability.)
When Alchemist's Talent enters, create two tapped Treasure tokens.
{1}{R}: Level 2
Treasures you control have "{T}, Sacrifice this artifact: Add two mana of any one color."
{4}{R}: Level 3
Whenever you cast a spell, if mana from a Treasure was spent to cast it, this Class deals damage equal to that spell's mana value to each opponent.