Gigantoplasm

You may have Gigantoplasm enter as a copy of any creature on the battlefield, except it has "{X}: This creature has base power and toughness X/X."

Clone

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

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

Volrath, the Shapestealer

At the beginning of combat on your turn, put a -1/-1 counter on up to one target creature.
{1}: Until your next turn, Volrath, the Shapestealer becomes a copy of target creature with a counter on it, except it's 7/5 and it has this ability.

Command Tower

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

Clone Legion

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

Mirrormade

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

Cryptoplasm

At the beginning of your upkeep, you may have Cryptoplasm become a copy of another target creature, except it has this ability.

Arcane Signet

Mind Unbound

At the beginning of your upkeep, put a lore counter on Mind Unbound, then draw a card for each lore counter on Mind Unbound.

Wall of Stolen Identity

You may have Wall of Stolen Identity enter as a copy of any creature on the battlefield, except it's a Wall in addition to its other types and has defender. When you do, tap the copied creature and it doesn't untap during its controller's untap step for as long as you control Wall of Stolen Identity.

Clever Impersonator

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

Sol Ring

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Sakashima of a Thousand Faces

You may have Sakashima of a Thousand Faces enter 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.)

Mirror Image

You may have Mirror Image enter as a copy of a creature you control.

Evil Twin

You may have Evil Twin enter as a copy of any creature on the battlefield, except it has "{U}{B}, {T}: Destroy target creature with the same name as this creature."

Mirror Mockery

Enchant creature
Whenever enchanted creature attacks, you may create a token that's a copy of that creature. Exile that token at end of combat.

Phyrexian Metamorph

({U/P} can be paid with either {U} or 2 life.)
You may have Phyrexian Metamorph enter as a copy of any artifact or creature on the battlefield, except it's an artifact in addition to its other types.

Rite of Replication

Kicker {5} (You may pay an additional {5} as you cast this spell.)
Create a token that's a copy of target creature. If this spell was kicked, create five of those tokens instead.

Spark Double

You may have Spark Double enter 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.

Mirage Mirror

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

Helm of the Host

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}

Dig Up

Cleave {1}{B}{B}{G} (You may cast this spell for its cleave cost. If you do, remove the words in square brackets.)
Search your library for a [basic land] card, [reveal it,] put it into your hand, then shuffle.

Exotic Orchard

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

Unstable Shapeshifter

Whenever another creature enters, Unstable Shapeshifter becomes a copy of that creature, except it has this ability.

Quasiduplicate

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.)

Shapeshifter's Marrow

At the beginning of each opponent's upkeep, that player reveals the top card of their library. If it's a creature card, the player puts the card into their graveyard and Shapeshifter's Marrow becomes a copy of that card. (If it does, it loses this ability.)