Sakashima of a Thousand Faces

You may have Sakashima of a Thousand Faces enter the battlefield as a copy of another creature you control, except it has Sakashima of a Thousand Faces's other abilities.
The "legend rule" doesn't apply to permanents you control.
Partner (You can have two commanders if both have partner.)

Cyclonic Rift

Return target nonland permanent you don't control to its owner's hand.
Overload {6}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Simic Signet

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Jade Avenger

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

Lotus Cobra

Landfall — Whenever a land enters the battlefield under your control, add one mana of any color.

Lignify

Enchant creature
Enchanted creature is a Treefolk with base power and toughness 0/4 and loses all abilities.

Hinterland Harbor

Hinterland Harbor enters the battlefield tapped unless you control a Forest or an Island.
{T}: Add {G} or {U}.

Burgeoning

Whenever an opponent plays a land, you may put a land card from your hand onto the battlefield.

Sol Ring

Birds of Paradise

Burrog Befuddler

Flash
When Burrog Befuddler enters the battlefield, target creature an opponent controls gets -1/-0 until end of turn.

Jace, Wielder of Mysteries

If you would draw a card while your library has no cards in it, you win the game instead.
+1: Target player mills two cards. Draw a card.
−8: Draw seven cards. Then if your library has no cards in it, you win the game.

Coiling Oracle

When Coiling Oracle enters the battlefield, reveal the top card of your library. If it's a land card, put it onto the battlefield. Otherwise, put that card into your hand.

Alchemist's Refuge

{T}: Add {C}.
{G}{U}, {T}: You may cast spells this turn as though they had flash.

Echoing Equation

Choose target creature you control. Each other creature you control becomes a copy of it until end of turn, except those creatures aren't legendary.

Augmenter Pugilist

Trample
As long as you control eight or more lands, Augmenter Pugilist gets +5/+5.

Augmenter Pugilist // Echoing Equation

Arcane Adaptation

As Arcane Adaptation enters the battlefield, choose a creature type.
Creatures you control are the chosen type in addition to their other types. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.

Metallic Mimic

As Metallic Mimic enters the battlefield, choose a creature type.
Metallic Mimic is the chosen type in addition to its other types.
Each other creature you control of the chosen type enters the battlefield with an additional +1/+1 counter on it.

Breeding Pool

({T}: Add {G} or {U}.)
As Breeding Pool enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

Yavimaya Coast

{T}: Add {C}.
{T}: Add {G} or {U}. Yavimaya Coast deals 1 damage to you.

Swan Song

Counter target enchantment, instant, or sorcery spell. Its controller creates a 2/2 blue Bird creature token with flying.

Deranged Assistant

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

Guardian Augmenter

Flash
Commander creatures you control get +2/+2.
Commanders you control have hexproof.

Exploration

You may play an additional land on each of your turns.

Manglehorn

When Manglehorn enters the battlefield, you may destroy target artifact.
Artifacts your opponents control enter the battlefield tapped.

Teferi, Mage of Zhalfir

Flash
Creature cards you own that aren't on the battlefield have flash.
Each opponent can cast spells only any time they could cast a sorcery.

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.

Excavating Anurid

When Excavating Anurid enters the battlefield, 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.

Song of the Dryads

Enchant permanent
Enchanted permanent is a colorless Forest land.

Universal Automaton

Changeling (This card is every creature type.)

Mesmeric Orb

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

Millikin

Misty Rainforest

{T}, Pay 1 life, Sacrifice Misty Rainforest: Search your library for a Forest or Island card, put it onto the battlefield, then shuffle.

Azusa, Lost but Seeking

You may play two additional lands on each of your turns.

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.)

Tatyova, Benthic Druid

Landfall — Whenever a land enters the battlefield under your control, you gain 1 life and draw a card.

Island

Desecrated Tomb

Whenever one or more creature cards leave your graveyard, create a 1/1 black Bat creature token with flying.

Slippery Bogbonder

Flash
Hexproof
When Slippery Bogbonder enters the battlefield, put a hexproof counter on target creature. Then move any number of counters from among creatures you control onto that creature.

Codex Shredder

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

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.)

Glen Elendra Archmage

Flying
{U}, Sacrifice Glen Elendra Archmage: Counter target noncreature spell.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Vedalken Orrery

You may cast spells as though they had flash.

Rejuvenating Springs

Rejuvenating Springs enters the battlefield tapped unless you have two or more opponents.
{T}: Add {G} or {U}.

Bloated Toad

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

Crocanura

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

Primal Surge

Exile the top card of your library. If it's a permanent card, you may put it onto the battlefield. If you do, repeat this process.

Wayward Swordtooth

Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
You may play an additional land on each of your turns.
Wayward Swordtooth can't attack or block unless you have the city's blessing.

Jace's Erasure

Whenever you draw a card, you may have target player mill a card.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Haze Frog

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

Galloping Lizrog

Trample
When Galloping Lizrog enters the battlefield, 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.

Drowned Secrets

Whenever you cast a blue spell, target player mills two cards.

Omnibian

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

Frogmite

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)

Flooded Grove

{T}: Add {C}.
{G/U}, {T}: Add {G}{G}, {G}{U}, or {U}{U}.

Perpetual Timepiece

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

Yavimaya, Cradle of Growth

Each land is a Forest in addition to its other land types.

Mystic Snake

Flash
When Mystic Snake enters the battlefield, counter target spell.

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.

Hedron Crab

Landfall — Whenever a land enters the battlefield under your control, target player mills three cards.

Forest

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.

Spore Frog

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

Fyndhorn Elves

Reclamation Sage

When Reclamation Sage enters the battlefield, you may destroy target artifact or enchantment.

Arcane Signet

Woodland Changeling

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Caustic Caterpillar

{1}{G}, Sacrifice Caustic Caterpillar: Destroy target artifact or enchantment.

Mothdust Changeling

Changeling (This card is every creature type.)
Tap an untapped creature you control: Mothdust Changeling gains flying until end of turn.

Amoeboid Changeling

Changeling (This card is every creature type.)
{T}: Target creature gains all creature types until end of turn.
{T}: Target creature loses all creature types until end of turn.

Vineglimmer Snarl

As Vineglimmer Snarl enters the battlefield, you may reveal a Forest or Island card from your hand. If you don't, Vineglimmer Snarl enters the battlefield tapped.
{T}: Add {G} or {U}.

Leyline of Anticipation

If Leyline of Anticipation is in your opening hand, you may begin the game with it on the battlefield.
You may cast spells as though they had flash.

Monstrify

Target creature gets +4/+4 until end of turn.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Talisman of Curiosity

{T}: Add {C}.
{T}: Add {G} or {U}. Talisman of Curiosity deals 1 damage to you.

Xenograft

As Xenograft enters the battlefield, choose a creature type.
Each creature you control is the chosen type in addition to its other types.

Laboratory Maniac

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

Scourge of Fleets

When Scourge of Fleets enters the battlefield, return each creature your opponents control with toughness X or less to its owner's hand, where X is the number of Islands you control.

Pongify

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

Thassa's Oracle

When Thassa's Oracle enters the battlefield, 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.)

Fleet Swallower

Whenever Fleet Swallower attacks, target player mills half their library, rounded up.

Sakura-Tribe Elder

Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Elvish Mystic

Bow of Nylea

Attacking creatures you control have deathtouch.
{1}{G}, {T}: Choose one —
• Put a +1/+1 counter on target creature.
• Bow of Nylea deals 2 damage to target creature with flying.
• You gain 3 life.
• Put up to four target cards from your graveyard on the bottom of your library in any order.

Venser, Shaper Savant

Flash
When Venser, Shaper Savant enters the battlefield, return target spell or permanent to its owner's hand.

Aesi, Tyrant of Gyre Strait

You may play an additional land on each of your turns.
Landfall — Whenever a land enters the battlefield under your control, you may draw a card.