For overland sets, which Mother's Sorrow is, weapons drop from WBs of the set's zone. And from chests.

"Overland Sets are sets that provide players with various bonuses when items of the same set are equipped simultaneously. Items constituting overland sets can only be found on monsters or in treasure chests in their respective zones. All overland sets are bind-on-equip. All sets will drop items for all armor and weapon slots, but only in a specific armor weight, as listed below.

Zones drop pieces from their sets:

Delve bosses drop a waist, foot, or unique item piece.
Overland bosses drop a head, chest, leg, weapon, or unique item piece.
Public dungeon bosses drop a shoulder, hand, weapon, or unique item piece.
Chests at Dark Anchors drop a jewelry set piece.
In Craglorn, these instead come from Anomalies.
In Summerset, these instead come from Abyssal Geysers.
Treasure chests chance to grant any set piece that can drop in that zone, increased by having the Treasure Hunter champion perk."

armymennl wrote: »

Hey people,
I see allot of diffrent answers to my quistion and want to know the right place it drops.
I need the flame staff of mother sorrow.
I know it drops in deshaan but from where only wb or also delves/ group dungeons etc.
I hope someone can answer me for my set.
Thanks already
ArmymenNL

I think you can get the infused mothersorrow staff from a quest in deshaan aswell. But I dont remember if it was a lighting or inferno staff.

DKMaestro wrote: »

Let me see.... it is around here somewhere. Oh yea - here it is:

http://lmgtfy.com/?q=ESo+where+find+mothers+sorrow

Lol that's funny!