There are treasures in this game! And they can be sold to shop keepers, either NPC or user run, or used to upgrade weapons, items for your characters or traded in for rare items in shops.
How does this work? Well, you earn treasures through dungeon runs and quests, and the better you do the more treasures you're awarded. Once you're dungeon run or quest is complete, the treasures will be added to your account along with your rupees and any items or heart pieces or magic upgrades you might have received during the quest or dungeon run.
Once you have enough treasures, you can sell them in the store to afford an item you really want, you can go buy more from Beedle's Shop, or you can go use them for upgrading your weapons and items so they can do more damage.
Your treasures are account wide, and are deducted by an admin or moderator once your purchase has been confirmed and accepted. What does account wide mean? That means any treasures you earn with one character can be applied towards a weapon upgrade on another character
Here are a list of treasures that you can get on this site, as well as their treasure classifications:
Super Rare Treasures
Blue Bird Feather
Chu Jellies (Only For Potions CANNOT BE SOLD)
Red Chu Jelly
Blue Chu Jelly
Purple Chu Jelly
Yellow Chu Jelly
Gold Chu Jelly
Green Chu Jelly
The ratios of finding these treasures in certain dungeons will be announced at the start of a dungeon topic, as the first post is usually made by admins to initiate what type of challenge you will be facing.
Treasures can also be bought from Beedle, but the rare the treasure the more expensive they are, and the more limited they are in numbers as well. So use your rupees wisely.
Also note that Chu jellies come only from Chu Chus and can only be used for the Gold Potion, or other potion shops that players open that require you to donate Chu jelly in order for you to make a potion.
That's all for now! Good luck finding treasures!