Keep

Keeps are large Structures near the Core.

Gameplay
Keeps will attempt to attack any enemy within their range. Normally, Keeps 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 Keep 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 Keep's range (by moving or through A Call For Help), it will instantly choose to retarget them. Otherwise, Keeps continues attacking the same target until it leaves its range, dies or in some other way becomes untargetable.

Keeps have True Sight, meaning they will reveal and attack stealthed Heroes. Keeps have a warmup period of 0.5 seconds before firing and must face their targets completely. Additionally, Keep'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 hte aggro by damaging defending enemy Heroes.

Destroying Forts and afterwards Keeps in a same lane is a massive objective because it makes the Core vulnerable to attack. In most maps (except Towers of Doom), destroying the lanes Fort and Keep will also cause that lane to spawn Catapults with every wavefor the attacking side.

Keeps deal 50% less damage to Summoned units.

Towers of Doom

 * In 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 Keeps on the map, the enemy Core will continuously take 1 point of damage every few seconds until the enemy team retakes a Keep.
 * 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 Keep awards 1,750 XP.

Trivia

 * Keeps had Ammunition until they were removed on December 12, 2017.
 * In Hanamura, prior to the July 11 2017 patch, destroying a Keep will spawn one unique Sapper minion for every other allied Minion wave. If this Sapper reaches the end of the lane, it'll do 1 point of damage to the enemy's Core. This is no longer the case, and destroying the Keeps will not spawn anything.