Cela, Mist Assassin

Cela, Mist Assassin gets +1/+1 for each Cela, Mist Assassin on the field.
Cela, Mist Assassin copies are nonlegendary.
If the original copy of Cela, Mist Assassin would
leave the battlefield, you may sacrifice another
Cela, Mist Assassin instead.
Cela, Mist Assassin may not be exiled from your
own effects.