It's been hard for me to test this particular spawn because I'm not sure how things are set up at the moment, but I just want to post this to double check for accuracy.
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The sarnak courier should spawn in the area circled in blue. North of the windmill to just passed the goblin ruins, but not up as far as the river to FV. He's not supposed to be particularly rare, but he is often unseen as he is in danger of being KS'd by the goblins in the area.
His spawn group is supposed to be comprised of uncharacteristically low level mobs for the area, and can have 3 or 4 PHs at any given time (so it's possible to have that many couriers up at once)
Here is the monklybusiness guide to popping him. 
	Quote:
	
	
		| Get a tracker and go to the mill...have him track one of these mobs: 
 A Goblin Brawler
 A Sabretooth Cat
 A Greater Scalbone
 A Sarnak Youth
 A Goblin Skirmisher
 A Greater Skeleton
 a sarnak courier
 an iksar marauder
 A Sarnak Flunkie*
 an iksar brigand**
 
 There will only be one of these mobs, they are lower level than all surrounding mobs between the mill and the lake...and possibly [probably not]as far as the sarnak fort(though they spawn at the mill area).
 When you kill one, another from that list will pop up on the druid's track after 1 minute. [other guides I've read have indicated it can be at low as 3 seconds] These are the PHs for the Courier. I can guarantee you will have your Courier in less than 30 minutes if you follow this procedure. It has been followed by many people and verified to work. Kunark has many of these type of rare cycles in most outdoor zones.
 
 *Flunkies are a rarer PH but if you can't find the cycle, clearing the Flunkies might be the ticket.
 **Brigands are the same as above, only rarer
 
 Edit: added the flunkies and brigands to the guide as I've been doing this cycle lately to get my enchanter a Goblin Gazhugi Ring. These are just a couple more mobs I've noticed. At one point today I had 5 couriers rotting at the same time.
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 I've cleaned the area out completely a few times over and have seen none of these possible PHs from the spawngroup, except for the Sabretooth Cat who spawns in that area, but only seems to respawn as a cat, or kit. 
So yea. double check these spawngroups for accuracy when you can, because this is an important spawn!