To obtain a Treasure Hoarder Insignia, you need to find and kill Treasure Hoarder at any level.
You can get these from any Treasure Hoarder you kill, no matter how they look or what they use to attack you. These Hoarders tend to roam around Liyue, though you can encounter them in Mondstadt during the Story Quests with Amber and on the outskirts of Dragonspine; Liyue is where they spawn.
The fastest way to get around is to use the Waypoints, kill everything in sight, and then move on. You can farm these about every two days; they do not respawn as quickly as monsters.
The image below is where you can find Treasure Hoarder Insignia in Liyue. The Golden Insignias are where the Hoaders spawn.
Just click on them to enlarge them.
- Type: Common Ascension Material
Treasure Hoarder Insignia is used for the following Character Ascension.
Each Common Ascension Material has three tiers; these are the next tiers after Treasure Hoarder Insignia.