Brinelin, the Moon Kraken {6}{U}{U}
Legendary Creature — Kraken
BlueCommander: legal
Identity
Blue
EDHREC rank
#5,508
Cheapest printing
US$0.24
TCGplayer
Printings
4
When Brinelin enters and whenever you cast a spell with mana value 6 or greater, you may return target nonland permanent to its owner's hand.
Partner (You can have two commanders if both have partner.)
Keywords: partner
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.