Proft, Sinister Mastermind {2}{B}
Legendary Creature — Human Rogue
BlackCommander: legal
Identity
Black
EDHREC rank
#27,353
Cheapest printing
US$0.12
TCGplayer
Printings
1
Threshold — You can't cast this spell unless there are seven or more cards in your graveyard.
Menace
{B}, Discard this card: Target creature gets -3/-1 until end of turn.
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.