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.

Deranged Assistant

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

Eternal Witness

When Eternal Witness enters, you may return target card from your graveyard to your hand.

Jade Avenger

Bushido 2 (Whenever this creature blocks or becomes blocked, it gets +2/+2 until end of turn.)

Burrog Befuddler

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, target creature an opponent controls gets -1/-0 until end of turn.

Bloated Toad

Protection from blue
Cycling {2} ({2}, Discard this card: Draw a card.)

Thassa's Oracle

When Thassa's Oracle enters, look at the top X cards of your library, where X is your devotion to blue. Put up to one of them on top of your library and the rest on the bottom of your library in a random order. If X is greater than or equal to the number of cards in your library, you win the game. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Mesmeric Orb

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

Traumatize

Target player mills half their library, rounded down.

Turn to Frog

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

Species Gorger

At the beginning of your upkeep, return a creature you control to its owner's hand.

Whiptongue Frog

{U}: Whiptongue Frog gains flying until end of turn.

Sol Ring

Galloping Lizrog

Trample
When Galloping Lizrog enters, you may remove any number of +1/+1 counters from among creatures you control. If you do, put twice that many +1/+1 counters on Galloping Lizrog.

Leapfrog

Leapfrog has flying as long as you've cast an instant or sorcery spell this turn.

Reflections of Littjara

As Reflections of Littjara enters, choose a creature type.
Whenever you cast a spell of the chosen type, copy that spell. (A copy of a permanent spell becomes a token.)

Excavating Anurid

When Excavating Anurid enters, you may sacrifice a land. If you do, draw a card.
Threshold — As long as seven or more cards are in your graveyard, Excavating Anurid gets +1/+1 and has vigilance.

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.

Anurid Barkripper

Threshold — Anurid Barkripper gets +2/+2 as long as seven or more cards are in your graveyard.

Omnibian

{T}: Target creature becomes a Frog with base power and toughness 3/3 until end of turn.

Steeple Creeper

{3}{U}: Steeple Creeper gains flying until end of turn.

Froghemoth

Trample, haste
Whenever Froghemoth deals combat damage to a player, exile up to that many target cards from their graveyard. Put a +1/+1 counter on Froghemoth for each creature card exiled this way. You gain 1 life for each noncreature card exiled this way.

Realmwalker

Changeling (This card is every creature type.)
As Realmwalker enters, choose a creature type.
You may look at the top card of your library any time.
You may cast creature spells of the chosen type from the top of your library.

Anurid Swarmsnapper

Reach (This creature can block creatures with flying.)
{1}{G}: Anurid Swarmsnapper can block an additional creature this turn.

Moritte of the Frost

Changeling (This card is every creature type.)
You may have Moritte of the Frost enter as a copy of a permanent you control, except it's legendary and snow in addition to its other types and, if it's a creature, it enters with two additional +1/+1 counters on it and has changeling.

Murkfiend Liege

Other green creatures you control get +1/+1.
Other blue creatures you control get +1/+1.
Untap all green and/or blue creatures you control during each other player's untap step.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Chub Toad

Whenever Chub Toad blocks or becomes blocked, it gets +2/+2 until end of turn.

Plaxcaster Frogling

Graft 3 (This creature enters with three +1/+1 counters on it. Whenever another creature enters, you may move a +1/+1 counter from this creature onto it.)
{2}: Target creature with a +1/+1 counter on it gains shroud until end of turn. (It can't be the target of spells or abilities.)

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.)

Whispersilk Cloak

Equipped creature can't be blocked and has shroud. (It can't be the target of spells or abilities.)
Equip {2}

Reclamation Sage

When this creature enters, you may destroy target artifact or enchantment.

Trollbred Guardian

{2}{G}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)
Each creature you control with a +1/+1 counter on it has trample.

Papercraft Decoy

When Papercraft Decoy leaves the battlefield, you may pay {2}. If you do, draw a card.

Crocanura

Reach (This creature can block creatures with flying.)
Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)

Spore Frog

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

Millikin

Masked Vandal

Changeling (This card is every creature type.)
When Masked Vandal enters, you may exile a creature card from your graveyard. If you do, exile target artifact or enchantment an opponent controls.

Orvar, the All-Form

Changeling
Whenever you cast an instant or sorcery spell, if it targets one or more other permanents you control, create a token that's a copy of one of those permanents.
When a spell or ability an opponent controls causes you to discard this card, create a token that's a copy of target permanent.

Haze Frog

Flash (You may cast this spell any time you could cast an instant.)
When Haze Frog enters, prevent all combat damage that other creatures would deal this turn.

Bloodline Pretender

Changeling (This card is every creature type.)
As Bloodline Pretender enters, choose a creature type.
Whenever another creature you control of the chosen type enters, put a +1/+1 counter on Bloodline Pretender.

Laboratory Maniac

If you would draw a card while your library has no cards in it, you win the game instead.

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.)

Perpetual Timepiece

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