Infected by Flood

When a soldier is attacked by Flood engineers, the engineers will first pierce their tentacles into the armor and through the skin and penetrate the spinal cord. Once inside the engineers will replace any useless body system unappealing to them. If the Marine is alive there will be extreme pain but they usually infect dead soldiers.

Once the body systems have been removed the head is moved aside to make room for tentacles to release more engineers. Then the Engineers will then determine