A Hero is a special unit that can be bought at a Capitol. Aside from Campaigns, the player can have only one living hero at the game. If this hero dies, the player can buy another one. There are two types of Hero: Strategist and Warrior. The two available Heroes change in every epoch.
The Strategist Heroes have the ability to heal other units, and they heal extremely faster than the Medics or hospitals. They also have good HP and decent attack, and can use the Battle Cry - which decreases an enemy unit's morale, making them more vulnerable (In short affected enemy units take more damage when attacked). Each age has it's own unique Strategist hero and such they can be upgraded once you age up.
The Warrior Heroes have higher HP and attack than the Strategists, however they cannot heal other units. Instead, Warriors provide morale bonuses to units near them much similar to houses around Town Centers or Capitals which will reduce the damage taken by player's units that are in the radius of a Warrior Hero. Warrior Heroes are also excellent fighters and can also act as a powerful fighting units.
Strategist Heroes were not supposed to attack. This is proven by the fact that they remain idle while getting attacked unless exclusively commanded to do so.
Both Warrior and Strategist heroes cannot be converted by priest