NPC vs NPC

[wolfwalkereci]

Off the top of my head this might work without having to perl script or lua script the fight:

If the main mob has a faction set him to be able to agro other npc's.
Create a unique faction for the spawned npc's that will agro the main npc.
Set the spawned npc agro range to be large enough they will go after the main npc target.
Set the spawned npc special_abilities to whatever you require if you do not want players to harm it.