Rex, Cyber-Hound {1}{W}{U}
Legendary Artifact Creature — Robot Dog
Identity
Azorius
EDHREC rank
#9,958
Cheapest printing
US$0.27
TCGplayer
Printings
4
Whenever Rex deals combat damage to a player, they mill two cards and you get {E}{E} (two energy counters).
Pay {E}{E}: Choose target creature card in a graveyard. Exile it with a brain counter on it. Activate only as a sorcery.
Rex has all activated abilities of all cards in exile with brain counters on them.
Keywords: mill
Every printing
highest TCGplayer market first; a card with only a thin single listing shows its low
In short
A Commander deck is a commander and 99 other cards, one copy of each (except basic lands), all inside the commander's colour identity. Paste a full list into the deck price calculator to price it and check it against the format.