One of the things I was able to rig on another server was ghost, ghouls, and familiars. .npc setspawn timer, despawn timer.
Lets set up my original phase as an example. Argent Crusade guards faction 2131 (friendly aggro enemies) aggro faction 21 (monster) as such paladins defend the gate from spawning ghouls and giests. As they aggro they fight eachother, die. and respawn. (mixed with aura with the birth spell effect to make ghouls crawl out of the ground) It adds a lively background asthetic for warzones.
Spawn timer allows to specific timing after death i.e. after death npc will spawn 40 seconds or almost 2 minutes for a retail server like npc death.
Despawn timer works for ghosts. If you have a haunted mansion phase you can combined with above command set npcs to spawn in and out and specific intervals. where they dissapear without requiring a actual death. Originally I had this rigged with a gobject. Gobject triggers the spawn [X]'s mirror image npc spawns, talks. despawns after 90 seconds like a recorded message. a friend of mine used this as a haunted maze phase with gobject teleporting pads on gilneas doors when clicked.
For the well versed player it can create an automated liveliness for a phase.