Similar to player company there are other mercenary units that take contracts for the living in Darklands.
They consist of highly skilled troops that are well armed and armored. This includes Swordmasters, Master Archers and Hedge Knights as well as standard mercenaries. Some bands also field Wardogs.
They are highly dangerous, and confrontation should be avoided, unless the company is up for a challenging fight with great loot. Also notice, that you will have a negative opinion penalty with a town or house, which hired a mercenary band if you dicide to attack one. This doesn't concern an event when delivering a cargo contract, in which you can also fight them, but will not have opinion penalty with anyone (and will not know who hired them or whether they acted independely). Anyway if you attack one mercenary band, others mercenaries will not pay attention on it - you will not have negative opinion with them.
Various mercenary companies can be found roaming around on the Global map and are also actively looking for and accepting Contracts from settlements. You are not the only mercenaries out there!