Crawling Infestation

At the beginning of your upkeep, you may mill two cards. (You may put the top two cards of your library into your graveyard.)
Whenever one or more creature cards are put into your graveyard from anywhere during your turn, create a 1/1 green Insect creature token. This ability triggers only once each turn.

Turn to Frog

Until end of turn, target creature loses all abilities and becomes a blue Frog with base power and toughness 1/1.

Argoth, Sanctum of Nature

This land enters tapped unless you control a legendary green creature.
{T}: Add {G}.
{2}{G}{G}, {T}: Create a 2/2 green Bear creature token, then mill three cards. Activate only as a sorcery.
(Melds with Titania, Voice of Gaea.)

Millikin

{T}, Mill a card: Add {C}. (To mill a card, put the top card of your library into your graveyard.)

Ghoulcaller's Bell

Ruin Crab

Landfall — Whenever a land you control enters, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)

Winds of Rebuke

Return target nonland permanent to its owner's hand. Each player mills two cards.

Cut Your Losses

Casualty 2 (As you cast this spell, you may sacrifice a creature with power 2 or greater. When you do, copy this spell and you may choose a new target for the copy.)
Target player mills half their library, rounded down.

Frogify

Enchant creature
Enchanted creature loses all abilities and is a blue Frog creature with base power and toughness 1/1. (It loses all other card types and creature types.)

Codex Shredder

{T}: Target player mills a card. (They put the top card of their library into their graveyard.)
{5}, {T}, Sacrifice this artifact: Return target card from your graveyard to your hand.

Shadow Kin

Flash
At the beginning of your upkeep, each player mills three cards. You may exile a creature card from among the cards milled this way. If you do, this creature becomes a copy of that card, except it has this ability.

Court of Cunning

When this enchantment enters, you become the monarch.
At the beginning of your upkeep, any number of target players each mill two cards. If you're the monarch, each of those players mills ten cards instead. (To mill a card, a player puts the top card of their library into their graveyard.)

Drown in Dreams

Choose one. If you control a commander as you cast this spell, you may choose both instead.
• Target player draws X cards.
• Target player mills twice X cards.

Croaking Counterpart

Create a token that's a copy of target non-Frog creature, except it's a 1/1 green Frog.
Flashback {3}{G}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Hedron Crab

Landfall — Whenever a land you control enters, target player mills three cards.

Mental Note

Spore Frog

Sacrifice this creature: Prevent all combat damage that would be dealt this turn.

Perpetual Timepiece

{T}: Mill two cards.
{2}, Exile this artifact: Shuffle any number of target cards from your graveyard into your library.

Crawling Sensation

At the beginning of your upkeep, you may mill two cards. (You may put the top two cards of your library into your graveyard.)
Whenever one or more land cards are put into your graveyard from anywhere for the first time each turn, create a 1/1 green Insect creature token.

Thought Scour

Target player mills two cards.
Draw a card.

Deranged Assistant

Grolnok, the Omnivore

Whenever a Frog you control attacks, mill three cards.
Whenever a permanent card is put into your graveyard from your library, exile it with a croak counter on it.
You may play lands and cast spells from among cards you own in exile with croak counters on them.

Sage of the Beyond

Flying
Spells you cast from anywhere other than your hand cost {2} less to cast.
Foretell {4}{U} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Mesmeric Orb

Whenever a permanent becomes untapped, that permanent's controller mills a card.

Rapid Hybridization

Destroy target creature. It can't be regenerated. That creature's controller creates a 3/3 green Frog Lizard creature token.

Halo Hopper

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)

Maskwood Nexus

Creatures you control are every creature type. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.
{3}, {T}: Create a 2/2 blue Shapeshifter creature token with changeling. (It is every creature type.)

Traumatize

Target player mills half their library, rounded down.

Brain Freeze

Target player mills three cards.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Cavern of Souls

As this land enters, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.

Altar of Dementia

Sacrifice a creature: Target player mills cards equal to the sacrificed creature's power.

Chronic Flooding

Enchant land
Whenever enchanted land becomes tapped, its controller mills three cards.

Zellix, Sanity Flayer

Hive Mind — Whenever a player mills one or more creature cards, you create a 1/1 black Horror creature token.
{1}, {T}: Target player mills three cards.
Choose a Background (You can have a Background as a second commander.)