Broken Skull Guardians are trolls, the land guards for Dulak's Harbor. They seem to be the only wandering mobs in the zone. Their patrol route takes them up and down the middle of the streets of the harbor, and they frequently stop at different stations on their path. If you find one of the safe hidey holes in the city to make camp in, you can pull the guardians back in them to fight with little fear of interference.
In about 15 kills, I've seen 2 compass notations and 1 insignia drop, in addition to the usual Broken Skull loot - various Zraxthil forged weapons, bucklers of Innoruuk and yummy troll parts.

Buckler of Innoruuk
Compass Notation
Consigned Simple Sealed Poison Vial
Crude Silk
Crystallized Sulfur
Damp Marrow
Emerald Ring
Fire Emerald
Fire Opal
Fulginate Ore
Insignia of the Blackblood
Mithril Amulet
Nilitim's Grimoire Pg. 115
Opal Bracelet
Pearl Necklace
Rough Animal Pelt
Rune of Attraction
Sapphire
Skirmisher's Shoulderguards
Star Ruby
Tears of Prexus
The Scent of Marr
Troll Parts
Zraxthril Forged Axe
Zraxthril Forged Cutlass
Zraxthril Forged Flamberge
Zraxthril Forged Mace