Some people still seem confused about the Mysterious Costume Trunk found in the Cash Shop - So I'm going to clear things up.
When you purchase the Mysterious Costume Trunk, and use it in your inventory, you get to choose which costume you'd like to have. That costume's trunk will appear in your inventory.
Using that trunk (the new Trunk of the Elven Kingdoms for example) will give you the choice of Male or Female.
You get all of the items in the set that you choose. So for example, if you open the male Trunk of the Elven Kingdoms you are given 9 items! (For just one trunk!)
Hopefully that clears some things up, since people get confused if they just get one item, if they get to choose, etc. :)