Mouthpiece is a ‘Boss’ in Borderlands 3. He is the first real boss as Shiv is pretty much just training wheels. You encounter Mouthpiece during the 3rd story mission, Cult Following, where you go to the Holy Broadcast Center. He’s the dubstep boss with all the speakers.
Mouthpiece is located in Ascension Bluff on the planet Pandora. You encounter him in the Holy Broadcast Center.
You can farm Mouthpiece for these legendary weapons as it is the dedicated loot source for these items. Mouthpiece has a ~18% legendary drop chance.
Mouthpiece can also drop the ‘Killing-Word’ this is a unique COV Pistol that shoots sound waves. Another unique drop is the ECHO-2 a Tediore grenade with a very high damage output and a 3 second fuse time.
Mouthpiece has a shield to protect himself, therefore, you need to attack him from the side or when he moves his shield out of the way. Mouthpiece will have a few immune phases where he will taunt you. During this moment, a section of the speakers in the arena will start charging up and explode. Look at the neon lights on the floor to see which section will explode. Stay clear of the area that is lit up as this will knock you back and can take you down. During the fight, there are a bunch of Tinks in the arena. You can use these to score a second wind. The Tinks will attack you when you get close to them but otherwise, they don’t pose much of a threat.