Also known as: 盗宝团, 宝盗団
"A ragtag group of bandits whose traces can be found all across the lands, even in deepest [sic] depths of uncharted domains.
Although their main purpose is hunting treasure, they are also known to get rough with unfortunate bystanders who happen to be nearby.
It's said that the group's founder, Reed Miller, defined the Treasure Hoarders as "an organization of mutual cooperation."
From ADVENTURER HANDBOOK
https://genshin-impact.fandom.com/wiki/Treasure_Hoarders