The upstart's downfall help plz

i defeated the boss and opened chest but how quest credit?

no one knows anything in this game?

what quest is that, can you give a little more information, like what zone or something ?

I think it’s this one:
The Breach: * The Upstart’s Downfall - quest can be obtained from Menudsjin at his camp(708, 1089).

‘Defeated THE boss’, but it looks like there’s a total of 3. Did you defeat all of them? or just the 1st one?