HP is a measure of how much damage an object can take before it is razed or killed. A unit's or building's HP is represented by a bar and a certain value. When the HP is reduced, the bar also gets depleted depending on the amount of HP that has been taken away. For example, a Villager in Age of Empires which has 25 HP has been attacked by a Heavy Horse Archer, whose damage input is 8. The Villager's HP on the initial attack drops to 17 (25-8=17). At the same time, the bar that corresponds to the Villager's HP gets depleted by about 1/3, to represent the remaining HP over the maximum HP (in this case, 17/25). If the HP reach 0, the bar gets fully depleted and the unit (building) dies (collapses) instantly. Various kinds of armor protect from some damage and therefore prolong the life of a unit or building. Also, there are a lot of technologies that can improve the HP of various units and structures.
The Explorer (in Age of Empires III) and campaign heroes in Age of Mythology and Age of Empires III faint when their hit points reach 1. They are therefore immortal and can be revived after a while. Some animals also remain as corpses and can be a food source until they run out or a natural decay eliminates the food available. However, in Age of Mythology, there is a possible glitch regarding this feature, wherein a villager may overlap a fallen hero's body or an animal's corpse by placing a building foundation on top of it. Once the construction has started, said body will be out of the game.
Regaining hit points Edit
Some units generally referred to as healers have the ability to heal friendly units up to their full health. That usually goes rather slow, but the more healers work together, the faster the healing goes.
In Age of Mythology, units cannot be healed by more than one healer, while some special and uniquely available units like the Son of Osiris, Nidhogg, or Titan cannot be healed at all. Meanwhile, the god power Regeneration, the Healing Spring-building created by a god power, and the Chinese myth unit Qilin are capable of healing all units within their range at once.
- Main article: Regeneration
In Age of Empires II, units garrisoned inside a building also automatically regenerate their hit points slowly. Units garrisoned inside Castle regenerate hit points twice as quickly than in other buildings. Researching Herbal Medicine quadruples the rate at which units regenerate inside buildings.
Buildings, siege weapons, and ships cannot be healed by a healer, but can still regain their HP by being repaired. As opposed to healing, however, repairing costs resources, but only half the initial price. In Age of Empires II, if a building is critically damaged, all garrisoned objects and units are ejected. They may re-enter that building once it has been repaired. This is no longer the case in Age of Mythology and Age of Empires III, where the building needs to be destroyed to eject the units.
In Age of Mythology, siege weapons and ships cannot be repaired but healed.
In Age of Empires III, siege weapons can be healed, ships are healed at the Dock, and buildings can be repaired by paying a price, which depends on the amount of hit points restored.