Unlock Location:
- Obtaining the
Onion requires you to defeat Sludgemaw during the side quest known as 'All Charged Up', which can be found as one of the faction missions in the Fadefields. - You may also receive the
Kickballer from the same boss.
Farm Method:
- Use Moxxi's Big Encore Machine to re-challenge Sludgemaw.
- Farm until the Onion drops.