Sin, Unending Cataclysm {5}{G}{U}
Legendary Creature — Leviathan Avatar
Identity
Simic
EDHREC rank
#4,932
Cheapest printing
US$0.24
TCGplayer
Printings
3
Flying, trample
As Sin enters, remove all counters from any number of artifacts, creatures, and enchantments. Sin enters with X +1/+1 counters on it, where X is twice the number of counters removed this way.
When Sin dies, put its counters on target creature you control, then shuffle this card into its owner's library.
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.