Omnath, Locus of the Void {7}
Legendary Creature — Elemental
ColorlessCommander: legal
Identity
Colorless
EDHREC rank
#10,675
Cheapest printing
US$3.13
TCGplayer
Printings
2
Omnath gets +1/+1 for each unspent mana you have.
If you would lose unspent mana, that mana becomes colorless instead.
Landfall — Whenever a land you control enters, add {C}{C}.
Keywords: landfall
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.