By npc I meant any ai that isn't a player, including prey and pets. I should've used ai to describe them instead. I apologize for causing a misunderstanding. There wont be any actual npcs in the game.
What I meant by my statement was that the difference between prey/pets and players wouldn't be distinguishable. That's why I was thinking of not including them. If a pack of wolves want to hunt an elk, how would they know if the elk is prey or a player? There would be a lot of harassment, even if by accident.
So, if a pack of wolves want to hunt an elk, they would have to pretend or find a player who is willing to play along. Players will be able to play as just about anything; when someone needs an elk, an actual elk would be available anywhere at anytime.
If players would want ai prey that badly, I think I would rather add a special token with infinite uses that spawns whatever you need. However, the token would be limited from one to five ai's at a time, limited to spawning ai's according to how many are in one area, timed for automatic despawn with a cushion time before respawning is allowed, and obtained by purchasing with real money (all to prevent spamming and overloading the server with spawned ai's).