ZDoom

My suggestion would be to add the actor who is responsible for spawning the entity. That way, for things like AEons of Death, the monsters that are spawned by directors can be given a watcher where, after a couple of minutes post-death, they can gradually fade out and not clutter up the map -- but only if spawned by the directors.

That is a bit of a specific example but still, this could prove to be very useful.

The Inflictor inside of WorldThingSpawned could be it.