This mob has 4 guards. They are all linked together. Pull one, you get them all. They work as a party. Master Nulim will heal his group mates that are getting hit. There is a caster looking healer as well. Suggest taking the two healers down first. The fighter/assassin types are much easier after the healers fall.
It seems that there should be a quest tied to these... I have yet to find one though.
Edit: If they are up that are at this /loc Queen's Labyrinth 36000 17360
The name might change, because it's freely tranlated from German into English. So it would be great if someone can confirm this. I'm Sorry about that :<