These are the mercenaries which used in War of Mercenaries, These units can be recruited at the Recruitment Chamber and hired at Hiring Quarters or the Central Hiring , The Mercenaries can also be trained (upgraded) at the Training Chambers, Also when you want to hire mercenaries you need at least one Mercenary Barracks to keep them in..
For more in-depth strategy purposes mercenaries do not come back to you Mercenary Barracks after combat, they can only be used 1 time in one battle even if they survive the battle. These are mercenaries and not your personal army keep that idea in mind.
There are 5 types of mercenaries in the game, each type fullfills a certain type of role in the game and excels at doing these roles.
The main roles are: