K-9, Mark I {U}
Legendary Artifact Creature — Robot Dog
BlueCommander: legal
Identity
Blue
EDHREC rank
#3,524
Cheapest printing
US$3.14
TCGplayer
Printings
6
Negative — As long as K-9 is untapped, other legendary creatures you control have ward {1}.
Affirmative — {1}{U}, {T}: Target legendary creature can't be blocked this turn.
Doctor's companion (You can have two commanders if the other is the Doctor.)
Keywords: negative, affirmative, doctor's companion
Every printing
highest TCGplayer market first; a card with only a thin single listing shows its low
Showcase · Surge Foil
K-9, Mark I
WHO · 1128
TCGplayer market
US$48.86
Extended Art · Surge Foil
K-9, Mark I
WHO · 953
TCGplayer market
US$7.37
Surge Foil
K-9, Mark I
WHO · 652
TCGplayer market
US$6.30
Showcase
K-9, Mark I
WHO · 537
Price not tracked
Extended Art
K-9, Mark I
WHO · 362
TCGplayer market
US$4.27
K-9, Mark I
WHO · 47
TCGplayer market
US$3.14
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.