Cryptoplasm

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

Shapesharer

Changeling (This card is every creature type.)
{2}{U}: Target Shapeshifter becomes a copy of target creature until your next turn.

Clone

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

Mistwalker

Changeling (This card is every creature type.)
Flying
{1}{U}: This creature gets +1/-1 until end of turn.

Argivian Avenger

{1}: Until end of turn, this creature gets -1/-1 and gains your choice of flying, vigilance, deathtouch, or haste.

Snow-Covered Island

Jodah's Avenger

{0}: Until end of turn, this creature gets -1/-1 and gains your choice of double strike, protection from red, vigilance, or shadow. (A creature with shadow can block or be blocked by only creatures with shadow.)

Bloodline Pretender

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

Flesh Duplicate

You may have this creature enter as a copy of any creature on the battlefield, except it has vanishing 3 if that creature doesn't have vanishing. (A permanent with vanishing 3 enters with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)

Aquamorph Entity

As this creature enters or is turned face up, it becomes your choice of 5/1 or 1/5.
Morph {2}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Morophon, the Boundless

Changeling (This card is every creature type.)
As Morophon enters, choose a creature type.
Spells of the chosen type you cast cost {W}{U}{B}{R}{G} less to cast. This effect reduces only the amount of colored mana you pay.
Other creatures you control of the chosen type get +1/+1.

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.

Malleable Impostor

Flash
Flying
You may have this creature enter as a copy of a creature an opponent controls, except it's a Faerie Shapeshifter in addition to its other types and it has flying.

Gigantoplasm

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

Clever Impersonator

You may have this creature enter as a copy of any nonland permanent on the battlefield.

Littjara Kinseekers

Changeling (This card is every creature type.)
When this creature enters, if you control three or more creatures that share a creature type, put a +1/+1 counter on this creature, then scry 1.