[Randymarsh9]

I feel like this would be the easiest way to do what you want. Say you are making an instance of a zone with version 1, then create two npcs. I'll refer to their IDs as npc1 and npc2. Spawn both of them in arbitrary locations in the zone and edit spawn2 to make sure they are in instance 1. On npc1, put a script like

sub EVENT_SPAWN{
 quest::signalwith(npc2, quest::ChooseRandom(1, 2, 3);
}

When the instance starts, this npc will spawn and randomly send a value of 1, 2, or 3 to npc2. On npc2, put this script

sub EVENT_SIGNAL{
 if ($signal == 1)
 {
   quest::spawn2(bossID, 0, 0, boss-x1, boss-y1, boss-z1, boss-h1);
 }
 if ($signal == 2)
 {
   quest::spawn2(bossID, 0, 0, boss-x2, boss-y2, boss-z1, boss-h2);
 }
 if ($signal == 3)
 {
   quest::spawn2(bossID, 0, 0, boss-x3, boss-y3, boss-z3, boss-h3);
 }
}

Be sure you have done #reloadquests before creating the instance, and it should work.