Nothing. Whether it be astral projection or a true O.B.E, there is no reason to believe that anything is able to "kill" or even injure the astral self during one of these states. If you experienced a death scenario, you were probably experiencing a lucid dream and not a true O.B.E, and despite the myth, you don't die just because you die in a dream.
You would die
you die
your body rots
You die
you die
You die
You die
You die.
well with my experience you die! DONT DO IT ciao
you die and do nothing, what an experience.
You will lose all the items in your inventory and your experience and respawn.
You die.