Mirage Mirror

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

Mimic Vat

Imprint — Whenever a nontoken creature dies, you may exile that card. If you do, return each other card exiled with Mimic Vat to its owner's graveyard.
{3}, {T}: Create a token that's a copy of a card exiled with Mimic Vat. It gains haste. Exile it at the beginning of the next end step.

Timberpack Wolf

Timberpack Wolf gets +1/+1 for each other creature you control named Timberpack Wolf.

Stangg, Echo Warrior

Whenever Stangg, Echo Warrior attacks, create Stangg Twin, a legendary 3/4 red and green Human Warrior creature token. It enters tapped and attacking. For each Aura and Equipment attached to Stangg, create a token that's a copy of it attached to Stangg Twin. Sacrifice all tokens created this way at the beginning of the next end step.

Stangg

When Stangg enters, create Stangg Twin, a legendary 3/4 red and green Human Warrior creature token. Exile that token when Stangg leaves the battlefield. Sacrifice Stangg when that token leaves the battlefield.

Mirror of the Forebears

As Mirror of the Forebears enters, choose a creature type.
{1}: Until end of turn, Mirror of the Forebears becomes a copy of target creature you control of the chosen type, except it's an artifact in addition to its other types.

Mirrorpool

Mirrorpool enters tapped.
{T}: Add {C}.
{2}{C}, {T}, Sacrifice Mirrorpool: Copy target instant or sorcery spell you control. You may choose new targets for the copy.
{4}{C}, {T}, Sacrifice Mirrorpool: Create a token that's a copy of target creature you control.

Gruff Triplets

Trample
When Gruff Triplets enters, if it isn't a token, create two tokens that are copies of it.
When Gruff Triplets dies, put a number of +1/+1 counters equal to its power on each creature you control named Gruff Triplets.

Pack Mastiff

{1}{R}: Each creature you control named Pack Mastiff gets +1/+0 until end of turn.

Mirror Box

The "legend rule" doesn't apply to permanents you control.
Each legendary creature you control gets +1/+1.
Each nontoken creature you control gets +1/+1 for each other creature you control with the same name as that creature.

Mirror Gallery

Brothers Yamazaki

Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.)
If there are exactly two permanents named Brothers Yamazaki on the battlefield, the "legend rule" doesn't apply to them.
Each other creature named Brothers Yamazaki gets +2/+2 and has haste.