Enter the zone and proceed south and east. You will have to use portals located in the zone to get to different parts.
There are several places around the zone that have trash mobs around green bubbles:
Clear trash around this named -969, 41, 766 .
Located at -1282, 34, 1050 . Again, a pretty easy fight. Clear whatever trash is in his room, then just burn him down. Occasionally, he will teleport you away from him. He will also put down large red rings (get out of them fast).
TIP: Turn off opacity for targeting rings to see his rings more easily
When he is killed, walk into the portal in the back of his room to be teleported to the northern most room on the map.
Located at -1282, 34, -531 . Very important.... TURN SINGULAR FOCUS ON There are adds during this fight. If you kill an add, Merrig goes back to full health and resets (but remains active). I had to kill him 4 times (without dying myself) before I turned on Singular Focus and it was easy as pie. Watch your target! Occasionally, Merrig will change your target to one of his adds. Once he is dead, proceed south to the next room. TURN SINGULAR FOCUS OFF
This is last part of Lab Crawl quest Hardest mob in the zone. Period. This is a DPS check, for the most part. When fighting him -969, 41, -247 , adds will spawn (break off of him). If you don't kill the adds, they will pile up on you (I think 6 is the maximum number of adds). These adds curse you and prevent you from casting damage spells (for my Wizard) and prevented my healer merc from casting beneficial spells (heals and cures). I ended up putting away my healer merc and used my Monk merc. Kept curing my Monk and DPSing named. Eventually I died, but Monk was able to finish named off. Very tough. I think I died 10 times before I was able to finish this guy. (Swashy note: Don't try to kite him...it doesn't work). Walk into portal in the back of this room Fly to the last named at the far East of the zone.
Note: the adds cast an arcane determent which stifles you, bring arcane cure potions if you can't cure yourself.
This fight happens in two stages. First, you burn him down (easy fight - don't hit him after he casts "Necromatic Sphere" as it will heal him (wait about 5-10sec)) and then a FAKE Exquisite Chest will drop. DO NOT click it until you are ready for the next stage. Barabes will revive and you fight him again. He's considerably harder this time and has adds. When the adds come, KILL THEM. They hit hard and will kill you. I think an add comes at each 25% mark. They don't have a whole lot of HPs. Once the last add is killed, Barabes hits much harder. Save your burst DPS / final burn until this point and get him from 25% to dead as fast as possible.