Mistform Ultimus {3}{U}
Legendary Creature — Illusion
BlueCommander: legal
Identity
Blue
EDHREC rank
#24,398
Cheapest printing
US$0.34
TCGplayer
Printings
2
Mistform Ultimus is every creature type (even if this card isn't on the battlefield).
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.