I was dressing up my HA and came back to find this item in my inventory: Mysterious Costume Trunk. I was wondering if someone could help me figure out where it came from and what it does. Should I open it or sell it? I'd hate to open it if there is just random junk inside. :/

It's an achievement prize for having X items in your wardrobe. Opening it will give you 500 CSC. c:

You can get it from an achievement for having so many items in your wardrobe, that's where it sounds like it came from.

I believe it no longer gives out costumes, but if you open it according to Subetalodge (I got mine a long time ago, I don't remember myself what was inside) you get a 500 credit gift card, which right now is just under 45 million if you want to sell or you can use it in the cash shop.

Thank you and thank you . I guess I'll just go ahead and open it then and hold on to the 500csc in case something tickles my fancy in the future. I appreciate you guys taking the time to answer me. Happy Monday!

You're welcome. :) You can check the achievements page to see what all you can get from each achievement if they have a star by it.