Afterlife

The Afterlife functions in some regards like a different plane. There are guardians of the afterlife that to the untrained eye look like skeletal giants. There is nothing in The Afterlife that was not once alive and now dead (including these guardians). Planeswalking to the Afterlife is indistinguishable from dying. Coming back to life is possible under certain circumstances (and what marks a successful planeswalk). They say planeswalking was invented as a way to connect with the Afterlife. It's hard to send someone to the afterlife in a way that they can be brought back, it's easy to sacrifice something and know it will be delivered to the Afterlife.