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.

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.

Identity Thief

Whenever this creature attacks, you may exile another target nontoken creature. If you do, this creature becomes a copy of that creature until end of turn. Return the exiled card to the battlefield under its owner's control at the beginning of the next end step.

Game-Trail Changeling

Changeling (This card is every creature type.)
Trample

Island

Mistwalker

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

Littjara Glade-Warden

Changeling (This card is every creature type.)
{2}{G}, {T}, Exile a creature card from your graveyard: Put two +1/+1 counters on target creature. Activate only as a sorcery.

Body Double

You may have this creature enter as a copy of any creature card in a graveyard.

Mocking Doppelganger

Flash
You may have this creature enter as a copy of a creature an opponent controls, except it has "Other creatures with the same name as this creature are goaded." (They attack each combat if able and attack a player other than you if able.)

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."

Glasspool Shore

Glasspool Mimic

You may have this creature enter as a copy of a creature you control, except it's a Shapeshifter Rogue in addition to its other types.

Glasspool Mimic // Glasspool Shore

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.)

Clever Impersonator

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

Masked Vandal

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

Altered Ego

This spell can't be countered.
You may have this creature enter as a copy of any creature on the battlefield, except it enters with X additional +1/+1 counters on it.

Volo, Guide to Monsters

Whenever you cast a creature spell that doesn't share a creature type with a creature you control or a creature card in your graveyard, copy that spell. (A copy of a creature spell becomes a token.)

Ego Erasure

Changeling (This card is every creature type.)
Creatures target player controls get -2/-0 and lose all creature types until end of turn.

Forest

Clone

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

Guardian Gladewalker

Changeling (This card is every creature type.)
When this creature enters, put a +1/+1 counter on target creature.

Jwari Shapeshifter

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

Cryptoplasm

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

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.

Moritte of the Frost

Changeling (This card is every creature type.)
You may have Moritte 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.

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.

Gladewalker Ritualist

Changeling (This card is every creature type.)
Whenever another creature you control named Gladewalker Ritualist enters, draw a card.

Mercurial Pretender

You may have this creature enter as a copy of a creature you control, except it has "{2}{U}{U}: Return this creature to its owner's hand."