Fort

Forts are fortified structures placed along the lanes in the Battlegrounds. They are bigger than Towers, but smaller than Keeps. When a team destroys a Fort, they’ll gain a Catapult in every 3rd Minion wave. This allows consistent (but not constant) pressure in a lane that enemies will have a hard time ignoring. Destroying a Fort also provides your team with a stacking 20% increase in Passively-earned Experience.

Gameplay
Forts will attempt to attack any enemy within their range. Normally, Forts prioritize attacking in order Objectives, then the closest Summon, Mercenary or Minion and finally the closest Hero, if no other units are in their range. However, if an allied Hero within the range of the Fort is being attacked by an enemy Hero in their range, A Call For Help is triggered, putting that Hero temporarily in the highest priority group. If a unit in higher priority group enters a Fort's range (by moving or through A Call For Help), it will instantly choose to retarget them. Otherwise, Fort keeps attacking the same target until it leaves its range, dies or in some other way becomes untargetable.

Forts also have True Sight, meaning they can reveal and attack stealthed Heroes. Forts have a warmup period of 0.5 seconds before firing and must face their targets completely. Additionally, Fort's attacks reduce Heroes Armor by 10, stacking up to -20 Armor. Players should let their minions tank the hits from this building and be careful of drawing aggro by damaging defending enemy Heroes.

Each team has one Fort in each lane (except on Towers of Doom). Next to the Forts are Towers, Healing Fountains, and strong Gates that prevent enemies from marching through them.

Early game advantage can be determined by who has destroyed more forts. Losing forts reduces the zone of safety and makes getting exp more dangerous. Forts represent the main form of progression within a match, with the destruction of enemy Forts and Structures serving to remove enemy defenses, allowing for unrestricted movement across the battlefield, and ultimately opening up access to the enemy Core, allowing the team to win the match. With bases heavily fortified, teams need to group up and make coordinated pushes in order to take down enemy Forts. Mercenaries such as Siege Giants and special vehicles such as the Dragon Knight can be very useful for swiftly demolishing Forts.

Forts deal 50% less damage to summoned units.

Towers of Doom

 * On Towers of Doom, destroying a Fort or Keep will allow the Altars activated by your team to do 1 more point of damage to the Core. If your team controls all 6 structures on the map, the enemy Core will continuously take 1 point of damage every few seconds until the enemy team retakes a structure.
 * The first time the Core of either team receives damage after 12:00, all forts upgrade to Keeps, including their Kill XP given.
 * Destroying a fort awards 1,200 XP.

Trivia

 * Forts had Ammunition until they were removed on December 12, 2017.