The Gadd’s Last Gizmo part where the Destroyer Matriarch, destroys the contentment fields is bugged. the NPC will destroy the right and left row but not the one facing the door. The NPC is invulnerable and cannot be killed.
According to many walk-throw guides and video all the rows most be destroyed in order to kill the NPC.
Walk-throw reference
https://www.youtube.com/watch?v=zFNSTdaH72g
Please fix, this is the last personal story to master.
Regards