Katagawa Ball is located in Skywell-27 on the planet Promethea. Run through the level, once you get inside the big building, you want to go down the elevator and stick to the left. There you will find another shaft to drop down into the boss fight.
You can farm Katagawa Ball for these legendary weapons as it is the dedicated loot source for these items. Katagawa Ball has a 30% legendary drop chance but 13.5% on M6 or higher.
Katagawa Ball Guide
Katagawa Ball fly above the arena making it a hard target to hit and giving itself a strategic advantage over you. During this fight you want to make good use of the cover in the arena. Peak, Shoot, and Hide is a solid strategy during this boss battle.
During the 1st phase, you want to use a corrosive weapon to strip away that armor bar. Then you have 2 more shield bars to deal with. Shock weapons are very effective against that. Aim for his eye to score critical hits.
During its 1st phase, Katagawa Ball will shoot Incendiary missiles but in its 2nd phase, Katagawa Ball will be smaller and adds Cryo to its arsenal. Don’t walk in those ice pools as they will slow you down and make you vulnerable to attacks. Katagawa Ball will also be able to heal itself during this phase. In the 3rd phase, Katagawa Ball adds corrosive to its arsenal.
There are very few additional enemies during this fight, making it hard to score a second wind when you are down. Stock up on ammo and bring a good shield before engaging in this fight.