Slime Against Humanity

Create a 0/0 green Ooze creature token with trample. Put X +1/+1 counters on it, where X is two plus the total number of cards you own in exile and in your graveyard that are Oozes or are named Slime Against Humanity.
A deck can have any number of cards named Slime Against Humanity.

Thought Scour

Target player mills two cards.
Draw a card.

Gale, Waterdeep Prodigy

Whenever you cast an instant or sorcery spell from your hand, you may cast up to one target card of the other type from your graveyard. If a spell cast from your graveyard this way would be put into your graveyard, exile it instead.
Choose a Background (You can have a Background as a second commander.)

Growth Spiral

Draw a card. You may put a land card from your hand onto the battlefield.

Inspiring Call

Draw a card for each creature you control with a +1/+1 counter on it. Those creatures gain indestructible until end of turn. (Damage and effects that say "destroy" don't destroy them.)

Charge Through

Target creature gains trample until end of turn.
Draw a card.

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Counterspell

The Ozolith

Whenever a creature you control leaves the battlefield, if it had counters on it, put those counters on The Ozolith.
At the beginning of combat on your turn, if The Ozolith has counters on it, you may move all counters from The Ozolith onto target creature.

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

Daze

You may return an Island you control to its owner's hand rather than pay this spell's mana cost.
Counter target spell unless its controller pays {1}.

Gitaxian Probe

({U/P} can be paid with either {U} or 2 life.)
Look at target player's hand.
Draw a card.

Mystical Tutor

Search your library for an instant or sorcery card, reveal it, then shuffle and put that card on top.

Muddle the Mixture

Counter target instant or sorcery spell.
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Stubborn Denial

Counter target noncreature spell unless its controller pays {1}.
Ferocious — If you control a creature with power 4 or greater, counter that spell instead.

Ideas Unbound

Draw three cards. Discard three cards at the beginning of the next end step.

Selvala, Heart of the Wilds

Whenever another creature enters, its controller may draw a card if its power is greater than each other creature's power.
{G}, {T}: Add X mana in any combination of colors, where X is the greatest power among creatures you control.

Emerald Medallion

Green spells you cast cost {1} less to cast.

Master Chef

Commander creatures you own have "This creature enters with an additional +1/+1 counter on it" and "Other creatures you control enter with an additional +1/+1 counter on them."

Ozolith, the Shattered Spire

If one or more +1/+1 counters would be put on an artifact or creature you control, that many plus one +1/+1 counters are put on it instead.
{1}{G}, {T}: Put a +1/+1 counter on target artifact or creature you control. Activate only as a sorcery.
Cycling {2} ({2}, Discard this card: Draw a card.)

Consider

Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
Draw a card.

See the Truth

Look at the top three cards of your library. Put one of those cards into your hand and the rest on the bottom of your library in any order. If this spell was cast from anywhere other than your hand, put each of those cards into your hand instead.

Worldly Tutor

Search your library for a creature card, reveal it, then shuffle and put the card on top.

Heroic Intervention

Permanents you control gain hexproof and indestructible until end of turn.

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Pongify

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.

Island

Sol Ring

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Baral, Chief of Compliance

Instant and sorcery spells you cast cost {1} less to cast.
Whenever a spell or ability you control counters a spell, you may draw a card. If you do, discard a card.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Mental Note

Decisive Denial

Choose one —
• Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)
• Counter target noncreature spell unless its controller pays {3}.

Forest

Sapphire Medallion

Blue spells you cast cost {1} less to cast.

An Offer You Can't Refuse

Counter target noncreature spell. Its controller creates two Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

Harrow

As an additional cost to cast this spell, sacrifice a land.
Search your library for up to two basic land cards, put them onto the battlefield, then shuffle.

Fabricate

Search your library for an artifact card, reveal it, put it into your hand, then shuffle.