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.

Lumbering Battlement

Vigilance
When this creature enters, exile any number of other nontoken creatures you control until it leaves the battlefield.
This creature gets +2/+2 for each card exiled with it.

Lagrella, the Magpie

When Lagrella enters, exile any number of other target creatures controlled by different players until Lagrella leaves the battlefield. When an exiled card enters under your control this way, put two +1/+1 counters on it.

Wormfang Drake

Flying
When this creature enters, sacrifice it unless you exile a creature you control other than this creature.
When this creature leaves the battlefield, return the exiled card to the battlefield under its owner's control.

Sakashima of a Thousand Faces

You may have Sakashima enter as a copy of another creature you control, except it has Sakashima's other abilities.
The "legend rule" doesn't apply to permanents you control.
Partner (You can have two commanders if both have partner.)

Spark Double

You may have this creature 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.

Glorious Protector

Flash
Flying
When this creature enters, you may exile any number of non-Angel creatures you control until this creature leaves the battlefield.
Foretell {2}{W}