NPC's

NPCs have many purposes including: NPCs are immortal and cannot die. Hitting them with a weapon will still reduce its durability. There appears to be no negative consequence for attacking an NPC.
 * Adding to story and lore via 'Talk' dialogue
 * Providing buying and selling merchant services
 * Providing useful information such as secrets and effects

Grave of Origin

 * Death (Temporary)

Mountain Base
The following NPCs can be found at this location:
 * Death
 * Dog #1
 * Dog #2

Gate of Purgatory

 * Death (Conditional)

Guardian Forest

 * Talkative man #1

Labyrinth Desert

 * Desert Merchant