From HoNwiki

Towers have a role of protecting their own units. Both the Hellbourne and Legion have eleven towers each. Three in each lane, and two neighbouring towers positioned at the center of each base, defending their most important building as known as the 'World Tree' (Legion) and the 'Sacrificial Shrine' (Hellbourne). A tower cannot be destroyed without destroying its predecessor. This means you cannot destroy the further away towers as long as the closer one is gone; this applies for each lane.

Basics

It is most helpful to destroy a tower with the help of allied creeps. This is because these buildings do a lot of damage, and attacking a vulnerable tower by yourself is an act of 'backdoor'. This is forbidden in tournament games unless it states so. In addition, attacking a tower by yourself without any nearby allies results in the tower healing itself.

A mininum of five towers must be destroyed before you can demolish the most important building that decides if you win or lose. This is achieved by destroying the three towers in one lane, then the two at the center.

All Towers have an attack range of 700. They also have a True Sight in a 900 radius around them, enabling them to see any invisible units.

Towers have:

• 1300/1600/1600/1600 health

• 18/18/25/30 armor and 0 magic armor

• 110/130/152/152 base damage

• Base Attack Time of 1/0.95/0.95/0.95

Tower Gold

If a tower falls, it gives a large amount of gold to the team that destroyed it. The reward is greater as the tower is closer to the enemy base. In the 2.5.8 patch, gold received for getting the last hit on Towers normalized from 452-470,502-520,552-570,602-620 to 460,510,560,610. The rest of the team gains 200/240/280/320 gold. If a creep destroys the tower, all heroes of that team gain 315/350/385/420 gold.

In Casual Mode, heroes do not get the bonus gold if he last hits a tower. However, gold from buildings are increased by 50%. Towers also give 150/200/250/300 experience globally to the team that destroyed it, even if a hero is dead.

Tower Behaviour

Tower only changes its target whenever the current target dies or leaves the tower range, or an enemy unit attacks an allied hero.

It prioritizes its targets in the following order

• Protecting an allied hero from an enemy attacking it, prioritizing a hero over a creep. - Spells do not trigger the aggro, and attacking in this case means starting your autoattack animation. You draw the aggro when your hero actually lifts his arm to launch an attack.

• The tower will attack nearby units with priority on units attacking it, and the closest target after that.

• Siege machines have a lower priority regardless of the distance from the tower.