
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 Box has 6 printings, first in Kamigawa: Neon Dynasty (2022). EDHREC ranks it #1,721 among Commander cards. It appears most in Deadpool, Trading Card decks (11,313 on EDHREC). It has 5 official rulings.
Deck counts from EDHREC.
Cards that show up in the same decks on EDHREC.