Buildings

Buildings are special units that are immune to most spells, use Structure Armor, and are immobile. Destroying a building rewards you with a bounty, similar to most Creeps or Heroes. Destroying towers rewards the entire team. Buildings are divided into several categories, each with their own role.

Towers
Each faction's three lanes are guarded by 3 towers, and their ancient guarded by 2 neighboring towers. Towers are referred to as "tier 1," tier 4," etc., with tier 1 towers being the ones closest to the river.

Every tower, except for tier 1 towers, is invulnerable until the tower preceding it is destroyed. The two towers defending a team's ancient become vulnerable if any tier 3 tower is destroyed. Note: No barracks have to be killed to make these towers vulnerable. Both of the tier 4 towers must be destroyed in order to remove the Ancient's invulnerability.

All towers have a sight range of 1900/800, and an attack range of 700. All towers deal Siege Damage, which deals only 85% damage to Heroes, but 150% damage to all siege Lane Creeps. Additionally, all towers have true sight in a 900 area around them, allowing them to see any invisible units including Observer Wards and Sentry Wards.

Towers can be denied, just like creeps, once they have 10% health or less. This means that tier 1 towers (1300 total HP) can be denied at 130 health or lower, and tier 2-4 towers (1600 total HP) can be denied at 160 health or lower. Denying towers reduces the gold bounty gained by the enemy team.

Towers have a specific targeting priority that determines which enemy it will attack. This list represents that priority in descending order:
 * 1) Closest enemy unit or hero attacking a friendly hero
 * 2) Closest enemy unit or hero attacking the tower itself
 * 3) Closest enemy unit or hero attacking any other friendly unit
 * 4) Closest enemy unit
 * 5) Closest enemy hero
 * 6) Closest enemy catapult
 * 7) Closest enemy ward

Note that in the above list, catapults and wards are exceptions, always being targeted after other units, even if they are attacking a friendly hero or the tower. Furthermore, towers attacking a catapult or ward will automatically switch to any other valid unit that enters their range (and towers attacking a ward will automatically switch to a catapult entering the range if it is the only other valid target). For any other unit, the tower will finish killing its current target before acquiring a new one.


 * There is one exception, which comes from an enemy unit attacking or issuing an attack order on a friendly hero. When this happens, all nearby friendly computer-controlled units, including towers, will immediately switch targets to the aggressor. This special aggro has a 2 second cooldown, allowing players to issue an attack outside tower range, then move into range, and issue another attack without drawing aggro.

Otherwise, the tower will only switch targets under four circumstances:
 * If the targeted enemy dies
 * If the targeted enemy moves out of the range
 * If the targeted enemy issues an attack order on a friendly unit or hero

When the tower switches targets, it will choose a new target based on the above priority list. In the third case, if the previous target is still the highest priority, it will continue to attack it.

When an enemy tower is destroyed, all allied heroes receive the tower's bounty as reliable gold.

If a hero gets the last hit on a tower, he receives an additional 150-250 unreliable gold.

If a tower is denied, the team bounty is halved, and no last-hit bounty is awarded.

Ancients
Ancients are massive structures found inside each faction's base. In order to win, each team must destroy the enemy team's Ancient. Ancients have no offensive abilities themselves, but are guarded by 2 Towers. They cannot be attacked until both Towers are destroyed.

Ancients have 4250 hit points, and regenerate 3 hit points/second. Ancients also have 15 armor, 1800/1800 sight range, and True Sight in a 900 area around them.

Barracks
Barracks are special buildings, defended by Tier 3 Towers, that are responsible for keeping Lane Creeps as powerful as their counterparts. There are two Barracks for each lane per faction - one for Melee Creeps, and one for Ranged Creeps. Destroying either Barracks provides a large boost to the destroying team's associated Lane Creeps, increasing their statistics, as well as reducing the gold and experience they give when killed.

Barracks are invulnerable until the Tower that is guarding them is destroyed. Melee Barracks have 1500 hit points 5 HP/sec regeneration, while Range Barracks only have 1200 hit points and no regeneration. Barracks also have 900/600 sight range. Destroying a melee barracks grants every player on the team 275 reliable gold, while destroying a range barracks grants 225 reliable gold; if a player unit gets the last hit, that player receives an additional 100-150 unreliable gold bounty. Barracks do not have True Sight, but do have backdoor protection.

Fountains
Fountains are Buildings located in the respawn areas of both bases, and provide healing and mana regeneration to all allied units near it. They also attack any enemy unit that comes within 800 range, dealing 190-199 physical chaos damage per attack. Together with their BAT of 0.15 this means that the fountain will deal around 970 DPS (before armor reductions) to the enemy heroes. Fountains have a True Sight radius of 1200. They are also invulnerable.

Subsidiary Buildings
In addition to the above Buildings, there are other Buildings that have no special function within a base. These Buildings exist only to occupy enemy creeps and to provide enemy players with gold.

On the whole, there are 15 of such buildings on each side. The five buildings closest to the team's Ancient can be made into effigies by using a cosmetic item. These are functionally identical to other buildings, but have a different appearance and display a text notification when destroyed.

Buildings have 500 health, 10 armor (fortified), and backdoor protection. They also have a sight range of 800/550 and give a 102-120 unreliable gold bounty when destroyed.

Backdoor Protection
All buildings except for the Tier 1 Towers possess the passive ability backdoor protection. Backdoor protection activates when there are no nearby enemy creeps in approximately an 800 radius, and causes the building to take 25% damage from illusions and 75% damage from other units. If a backdoor-protected building is damaged by an enemy, it will regenerate the lost health at a rate of 90 HP per second. It is still possible to destroy protected buildings with sufficiently high damage. Backdoor protection will not regenerate damage dealt by friendly units.

On the Tier 2 Towers, backdoor protection is independent of each tower. For the Tier 3 towers, Barracks, the Ancient, and subsidiary buildings, if the backdoor protection goes down for any one building in a base, it is deactivated for all of them.

Backdoor Protection is restored approximately 15 seconds after the death of the last creep in range.

Glyph of Fortification
The Glyph of Fortification is an ability usable by any player on a team that renders all buildings owned by their team invulnerable and spell immune for a short duration. It can only be used once every 5 minutes, and lasts for 5 seconds. The Glyph can be used to stop enemy pushes, or slow them down long enough to organize a defense.

Cooldown is refreshed whenever you lose a Tier 1 tower.

Abilities that Affect Buildings
The following abilities can target or damage buildings.

Most hero abilities that deal physical damage are considered Hero damage and are reduced by 50% against Structure armor as well as standard armor value reductions.