The cost of training a unit is by default 3 times the usual cost of the unit it is trained into. The Training Grounds, the base building that makes Training possible, sets a limit at 7 units per week, while the Hall of Heroes upgrade increases that number to 20. There is also a weekly limit to the number of units that can be trained in a specific town, depending on which Training support buildings have been built in-town.
For example, Peasant to Archer to Footman to Priest, as is detailed in the costs table below. Of course, you're not bound to stop there, and can go on up the ladder. Of Haven's 7 creature levels, 5 are comprised of humans, giving you 4 possible upgrades. The entire Training process can only be executed by Knights, i.e., Haven Heroes. Training allows the player to convert a human unit of a lower level into a human unit of a higher level - at a price.
Haven's Racial Skill, Training, takes advantage of the town's predominantly human forces.
