The Hero Academy is an Advanced Building that can be used to train or "retrain" Heroes, Trainer Heroes, and Troops of varying rarities.
Once your Stronghold reaches Level 25, one Mine, Farm, Training Camp, or Forge in your base may be converted to (and back from) the Hero Academy. The building being converted must be Level 5 or higher. Iron is only used in the first conversion; subsequent ones are free.
The Hero Academy can be upgraded up to Level 10. Training and research cannot be conducted during upgrades. Once the building reaches Level 2, it can either conduct two different Trainings in parallel, or conduct one type of Training while also researching a new recipe. It cannot research two different recipes in parallel.
Below is the list of recipes that become researchable at each level:
- Level 1: Train Common Heroes
- Level 2: Train Common Troops
- Level 3: Train Uncommon Heroes
- Level 4: Train Uncommon Troops
- Level 5: Train Rare Heroes
- Level 6: Train Rare Troops
- Level 7: Train Trainer Heroes
- Level 8: Train Epic Heroes
- Level 9: Retrain Epic Troops
- Level 10: Retrain Legendary Heroes
There is a chance to obtain certain non-Classic Heroes from Level 5, Level 8, and Level 10 Trainings. These Heroes are specified within the dialog window that pops up when you tap "Train" — you can see the list by tapping the blue circle icon with an "(i)" in the top left corner.