Voices from the Darkness is a quest that you will receive from Wardek after completing The Lost Father quest. Our Elex 2 game guide will walk you through all the stages of the quest.
Conversation with Thialg
First, talk to the berserker named Thialg - he can be found in the Bastion. He will provide you with the information necessary to continue the quest.
Factory near the Depository
The destroyed factory near the Depository will be marked on your map. Go there. You can shorten the journey by teleporting to the above-mentioned Depository.
Once there, find the brick building from the screenshot above and enter it. A cut-scene involving the CRONY U4 drone will play and then you will have a conversation. At this point, the Voices from the Darkness quest will be completed automatically.
Note - after the dialogue is over, you will be attacked by two Curators.