I'm afraid that it is not currently possible to have NPC's attack each other in Coldstone created games. There are essentially two types of NPCs: passive, and aggressive. The passive ones are the kind that make up the shopkeepers, people etc. of the world, whilst the aggressive ones are those who attack the player. There is currently no way to make NPC's that would either aid the player, or attack other NPCs.
Apparently this feature is technically supported by Coldstone, but the user cannot access it. Hopefully it will be addressed some time later, with a patch or somesuch.
-Andiyar
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"Any good that I may do here, let me do now, for I may not pass this way again"