Little is known about the Adventurers Guild yet but characters from it were introduced with version 0.58.3. Named NPCs from the group can be found in random locations around the map. Spotting of its members is most likely to occur near Cannibals villages, where an adventurer was likely captured and carried into a cage.
If rescued or encountered anywhere else the member will behave similar to any other NPC. If talked to you will get the typical response, "If you're looking to hire someone, try asking around in bars." Left alone the adventurer will wander between shops with the goal "shopping".
Adventurers also appear to be equipped with different gear and weapons with no set uniform for the group.