Borderlands 3Hostile Takeover

"Hostile Takeover" is the 6th Main Story Mission and is unlocked when you complete "Sanctuary".
An additional Null Pointer Sniper Rifle is found in a Chest at the end of the Quest.

The Calypsos want to open a Vault on Promethea, so we need to beat them to it. We’ll need to make friends with Atlas Corporation if we want to find the Vault. But Atlas has its own set of megacorp-sized problems that could be solved by a gun-wielding go-getter such as yourself.