Add a side branch that can only be entered by dying in a certain place such as the Valley of the Dead, or by life saving not working. When you die, you appear there with no inventory and have to fight your way out to return to your body. Monsters are also subject to this and appear in that branch after dying to the same conditions. However, it only works once - if you die again you die for good, even if you successfully got back to your body in the process.