Rex, Cyber-Hound is a rare Legendary Artifact Creature — Robot Dog card from Fallout (PIP), collector number 427. Current market price: $0.90 (foil $0.97), TCGplayer market prices via Scryfall.
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.