For each attacking creature, its owner puts it on the top or bottom of their library.

Each player sacrifices all permanents they control that are one or more colors.

Create a token that's a copy of target creature you control.

Flashback {5}{U}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Whenever you draw a card, put a +1/+1 counter on Chasm Skulker.

When Chasm Skulker dies, create X 1/1 blue Squid creature tokens with islandwalk, where X is the number of +1/+1 counters on Chasm Skulker. (They can't be blocked as long as defending player controls an Island.)

You may have Clever Impersonator enter the battlefield as a copy of any nonland permanent on the battlefield.

For each creature target player controls, create a token that's a copy of that creature.

Whenever an opponent shuffles their library, you may put a +1/+1 counter on Cosi's Trickster.

Enchant creature

Enchanted creature gets +1/+1 and has "Whenever this creature deals combat damage to a player, you may draw a card."

At the beginning of your end step, if you didn't attack with a creature this turn, sacrifice Curious Obsession.

Exile X target creatures. For each creature exiled this way, its controller creates a 2/2 green Boar creature token.

Sacrifice Cursecatcher: Counter target instant or sorcery spell unless its controller pays {1}.

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.")

Level up {1}{U} ({1}{U}: Put a level counter on this. Level up only as a sorcery.)

LEVEL 1-2

0/1

{T}: Draw a card, then discard a card.

LEVEL 3+

0/1

{T}: Draw a card.

{T}: Add one mana of any color that a land an opponent controls could produce.

Whenever Hammer of Nazahn or another Equipment enters the battlefield under your control, you may attach that Equipment to target creature you control.

Equipped creature gets +2/+0 and has indestructible.

Equip {4}

You may cast Harbinger of the Tides as though it had flash if you pay {2} more to cast it. (You may cast it any time you could cast an instant.)

When Harbinger of the Tides enters the battlefield, you may return target tapped creature an opponent controls to its owner's hand.

At the beginning of combat on your turn, create a token that's a copy of equipped creature, except the token isn't legendary. That token gains haste.

Equip {5}

Flash

If an opponent would draw a card except the first one they draw in each of their draw steps, instead you create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Enchant creature, land, or planeswalker

Enchanted permanent is a colorless land with "{T}: Add {C}" and loses all other card types and abilities.

As Kindred Discovery enters the battlefield, choose a creature type.

Whenever a creature you control of the chosen type enters the battlefield or attacks, draw a card.

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.

Whenever a spell or ability you control counters a spell, you may create a 1/1 blue Merfolk creature token.

Tap seven untapped Merfolk you control: Counter target spell.

{T}: Draw a card, then discard a card.

Flash

When Merfolk Trickster enters the battlefield, tap target creature an opponent controls. It loses all abilities until end of turn.

At the beginning of your end step, untap all Merfolk you control.

{T}: Add {C}.

{1}, {T}, Sacrifice Mind Stone: Draw a card.

{2}: Mirage Mirror becomes a copy of target artifact, creature, enchantment, or land until end of turn.

You may have Mirrormade enter the battlefield as a copy of any artifact or enchantment on the battlefield.

Sacrifice Mistcaller: Until end of turn, if a nontoken creature would enter the battlefield and it wasn't cast, exile it instead.

If X is 1, scry 1, then draw a card.

If X is 2, you may choose a player. They return a creature they control to its owner's hand.

If X is 3, create a 4/4 blue and red Elemental creature token.

If X is 4 or more, do all of the above.

Equipped creature has shroud. (It can't be the target of spells or abilities.)

{U}{U}: Attach Neurok Stealthsuit to target creature you control.

Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

{4}, {T}: Put a fate counter on target permanent.

{5}, {T}, Sacrifice Oblivion Stone: Destroy each nonland permanent without a fate counter on it, then remove all fate counters from all permanents.

{T}: Add {C}.

{1}, {T}, Sacrifice an artifact: You gain 1 life.

({U/P} can be paid with either {U} or 2 life.)

You may have Phyrexian Metamorph enter the battlefield as a copy of any artifact or creature on the battlefield, except it's an artifact in addition to its other types.

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Create a token that's a copy of target creature you control.

Jump-start (You may cast this card from your graveyard by discarding a card in addition to paying its other costs. Then exile this card.)

Exile target artifact or creature. Its controller creates a 4/4 blue and red Elemental creature token.

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

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

{1}, {T}: Tap target land.

Return all nonland permanents target player controls to their owner's hand.

{U}: Rootwater Thief gains flying until end of turn.

Whenever Rootwater Thief deals combat damage to a player, you may pay {2}. If you do, search that player's library for a card and exile it, then the player shuffles.

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.)

You may have Sakashima the Impostor enter the battlefield as a copy of any creature on the battlefield, except its name is Sakashima the Impostor, it's legendary in addition to its other types, and it has "{2}{U}{U}: Return this creature to its owner's hand at the beginning of the next end step."

Flash

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom of your library in a random order.)

You may have Sakashima's Protege enter the battlefield as a copy of any permanent that entered the battlefield this turn.

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

Counter target spell.

Foretell {1}{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.)

{T}: Target creature gets -X/-0 until end of turn, where X is the number of Merfolk and/or Faeries you control.

You may have Spark Double enter the battlefield as a copy of a creature or planeswalker you control, except it enters with an additional +1/+1 counter on it if it's a creature, it enters with an additional loyalty counter on it if it's a planeswalker, and it isn't legendary.

When Specimen Collector enters the battlefield, create a 1/1 green Squirrel creature token and a 0/3 blue Crab creature token.

When Specimen Collector dies, create a token that's a copy of target token you control.

Flying

{2}: Steel Hellkite gets +1/+0 until end of turn.

{X}: Destroy each nonland permanent with mana value X whose controller was dealt combat damage by Steel Hellkite this turn. Activate only once each turn.

{1}{U}, {T}: You may tap or untap target creature.

{2}, {T}: Copy target triggered ability you control. You may choose new targets for the copy. (A triggered ability uses the words "when," "whenever," or "at.")

Flash

You may have Stunt Double enter the battlefield as a copy of any creature on the battlefield.

{U}{U}, {T}: Target creature gains shroud until end of turn. Activate only during your upkeep. (It can't be the target of spells or abilities.)

Svyelunite Temple enters the battlefield tapped.

{T}: Add {U}.

{T}, Sacrifice Svyelunite Temple: Add {U}{U}.

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

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

Equip {1}

Equipped creature gets +2/+0 and has first strike, vigilance, trample, and haste.

Equip {3}

Whenever you cast an instant or sorcery spell, create a 2/2 blue Drake creature token with flying.

When Tempest Caller enters the battlefield, tap all creatures target opponent controls.

{T}: Add {C}{C}. Activate only if you control five or more lands.

Indestructible

As long as your devotion to blue is less than five, Thassa isn't a creature.

At the beginning of your end step, exile up to one other target creature you control, then return that card to the battlefield under your control.

{3}{U}: Tap another target creature.

Indestructible

As long as your devotion to blue is less than five, Thassa isn't a creature. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

At the beginning of your upkeep, scry 1.

{1}{U}: Target creature you control can't be blocked this turn.

At the beginning of your end step, each opponent loses life equal to the number of tapped creatures you control.

{T}: Target land becomes an Island until end of turn.

{T}: Target land becomes the basic land type of your choice until end of turn. Activate only during your turn.

You may have Vesuvan Doppelganger enter the battlefield as a copy of any creature on the battlefield, except it doesn't copy that creature's color and it has "At the beginning of your upkeep, you may have this creature become a copy of target creature, except it doesn't copy that creature's color and it has this ability."

You may have Vizier of Many Faces enter the battlefield as a copy of any creature on the battlefield, except if Vizier of Many Faces was embalmed, the token has no mana cost, it's white, and it's a Zombie in addition to its other types.

Embalm {3}{U}{U}

Return all creatures to their owners' hands except for Krakens, Leviathans, Octopuses, and Serpents.

Flying

As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.