I found a Shadowglen map piece as a random event. I have an OLD account, but I haven't played in a while and I've never done the maps so I don't know if the thing is worth keeping or not.

The entire set is worth 6 million, which I'm only willing to invest in a map if it's worthwhile.

Is it worth keeping? Is it worth collecting the other pieces? What kind of prizes do you get from the shadowglen treasure hunt? How often can you get prizes?

The prize, as far as I know, is the treasure map pieces. They're wearable, pirate themed items. Keep them if you want to wear them, sell them if you don't care. I don't -THINK- the maps lead anywhere, unless staff has a trick hidden up their sleeve.

These maps are part of a Scavenger Hunt. There are three sets of 5 pieces each that can be found while doing a sequencies of acts here on Subeta. They are merely pirate-themed wears (unless, like Squid said, staff does stuff with them later on). I really don't hope so because I sold some of mine

The announcement post for the Scavenger Hunt point-blank said that they will get these maps for sale somewhere somehow after the event is over. Therefore they will not be exclusive for very long. We've also been told in the Comments for that announcement post that finding all the pieces is all there is there is no Achievement or extra prize for completion or owning complete sets. Sell them now if you like, but you are gambling that the price that they set will be lower than the price you are selling them for if you think maybe later you're gonna want the pieces. Keep them if you like, with the understanding that they won't get any more valuable than the price that they will be set at when they are re-released outside of the event.