To obtain the Bursa Obscura 
you must have 55 Tentacles Pieces. 
You can get 11 Tentacles Pieces from the Mini World Change “Rise of Devovorga” or they can also be obtained from the Market.
Once you have all 55 Tentacles Pieces, you must head to the NPC Malunga 
located in Liberty Bay.
Follow the map below to find it:
Once you reach the marked area, you must climb 2 floors and thus be able to find Malunga. When you find it you must say “Hi, Bursa Obscura, Yes” and in this way you will get your Bursa Obscura, this backpack contains 1 slot for imbuiment.
