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.

The Echo is a topsy turvy reflection of the plane where life souls wander about playing out a strange little version of what they did in life. Necromancers can dip into it for life souls they need.

How do inanimate things die? When it ceases to be recognized as what is was. So it's about external judgement, at least for inanimate objects.

When creating a new object you can put the dead soul of an inanimate object into it instead of letting it form it's own new soul (i.e a sword with the soul of a famous mountain). Mashing souls into things is realllllly delicate work that can go wrong if you're not careful.