Servants of Mistmoore have extremely small aggro radii for players. They're more interested in killing the Renda'Dal mobs. Their Vampiric Touch ability, which is unremarkable when used on a PC, hits the Renda'Dal for massive damage. This isn't normally a problem, but if you're camping a named monster in an area where Mistmoore servants spawn, there's a chance of the Mistmoore servant killing the namer before you get to it!
Servants of Mistmoore are triggered spawns at night in the narrow passes leading to the deeper sections of the zones. They don't automatically aggro, so if you're looking to avoid fights stay near the middle of the path and they'll leave you alone.
This mob has been identified as an excellent choice of charm pet for Coercers.