Activate the ritual stone to gain the ability to revive the surrounding bodies once a day, and then go to the end of the old demon. After entering the door, wait four to five seconds with the effect of ritual stone before going out. You will see the assassin of the Dark Brotherhood resurrect around you, chop him to death, and pick up equipment (you can put something on him to ensure that the body will not disappear, and when he resurrects one day later, you can sell clothes indefinitely).