yeah. A.I.
I suppose this is exactly what I suggested/predicted after seeing scribblenauts the first time.
Everything is given tags.
Like a lit torch would be something like [plant,dead,wood,fire,oil]
These tags then create AI behaviours, as well as interaction.
A troll might be something like [animal,intelligent,fire:hate,fire:fear,use:club,li ve:cave,spider:hate,food:like] attributes, and behaviours related to attributes. Trolls fear fire, and will either run from, or try to put it out. While throwing food on the ground might lure them into traps, or even distract during a fight.
The other problem here is this is simulation territory, NOT combat. simcity does not make a very good RTS. NPCs behaving in sim ways. dwarf fortress, gnomoria, etc do not really make good engaging player challenges. does the sim AI go on hold when combat engages? Hunting npcs to extinction, etc is what happens when players are let loose on simulations. there is a reason why games do not do that. Players quickly game the system, so its much better to have static spawns, etc.