Hi,
For this achievement you need to collect 6 unique costumes and wear them at the same time.
Here is a list of the costumes and where to find them. All of them can be found in three worlds: Outskirts, The Mine and Skyraft. I will add some videos of these world below the lists. Some of these costumes are quite tricky to get, so if you have problems getting them refer to the videos.
1. Weapon of Choice = level 2-4 (Outskirts IV)
2. A.R.E.S. helmet = level 2-7 (Outskirts VII)
3. Lumi = level 3-4 (The Mine IV)
4. Tetro ME = Level 3-7 (The Mine VII)
5. Dead Samurai = level 4-4 (Skyraft IV)
6. Ahrah Wielder = level 4-7 (Skyraft VII)
Outskirts: The MineSkyraft(video credit: Macktion)
Hope this helps :-)
Any improvements ? Plese let me know in the comments below!