There is 1 Dead Ghost to be found in N/Gen Branch. They can be collected on the Strike Mission: The Nexus. Each Ghost can only be collected once per account.
Ghost 1[edit]
Head out into the N/Gen Branch during the Strike mission. You will called to go up some stairs after you have cleared this area of enemies. Just head on up the stairs.
Before you go into the building, head over to the left of the door. Look just to the left of the terminal by the door. On the ground you will find the Dead Ghost you are looking for:
