Arthur, Marigold Knight {2}{U}{R}{W}
Legendary Creature — Mouse Knight
Identity
Jeskai
EDHREC rank
#8,174
Cheapest printing
US$0.37
TCGplayer
Printings
2
Haste
Whenever Arthur and at least one other creature attack, look at the top six cards of your library. You may put a creature card from among them onto the battlefield tapped and attacking. Put the rest on the bottom of your library in a random order. Return that creature to its owner's hand at end of combat.
Keywords: haste
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.