DH:A will feature mercenary (or "merc") units on some maps. The merc races replace the original game's non-playable races. Just like the mod's four main races, merc races have their own special abilities, advantages, and weaknesses. Merc ships often take less time to deploy than the main races' vessels.
To hire merc units, the player must capture derelict "shipyards." Then these shipyards must be defended in order to keep mercenary units coming in.