The Gnosis is a small chess piece that represents an element, one of seven, to be in an Archon's possession. Genshin Impact has built wonderful lore and thought out every piece and tidbit of story it puts into the game. Genshin Impact's Gnoses are some of, if not the most, powerful items in all of Teyvat. They are what "makes" an Archon. These tiny artifacts were rewarded to the seven Archons after the Archon War long ago.