Tower Behaviour / Aggro Guide

This guide aims to provide more information on how buildings behave, and how to respond to that behaviour.

Introduction

More often than not, people will say: "Gosh, the tower always switches to me when I go under it! Funny thing is, it never switches when my enemy goes. Haha." or "If ONLY the tower did switch to that hero, I'd have killed him!", as if randomness took its place in the decision of a tower's target. Well, first things first:

RANDOMNESS IS THE LEAST IMPORTANT FACTOR IN THE DECISION OF A TOWER'S TARGET!

Meaning: Tower has priorities, and randomness only takes its place if you are sharing a "priority level" with someone else. And even so, as you shall see in this guide, it is not "random" in fact. So, arguably, we could say that there is NOTHING random in a tower's decision to attack.

That said, I strongly believe that knowledge about tower aggro (and creep aggro, which is essentially the same) is the most important step between low level of gameplay and intermediate level of gameplay. After getting to know heroes and having some intuition over the game, this should be what you strive for. Although it is only a opinion, it may have some value to consider.

Tower Priority

Let's talk about what matters, and what is the skeleton of this guide: The tower priority.

I'll explain how it works in three different ways: List, Illustrative and Program-like.

List

This is the priority list for a tower's target, with 1 being top priority:

1. Closest enemy hero attacking a friendly hero with auto attack
   
2. Closest enemy creep attacking a friendly hero with auto attack
   
3. Closest enemy creep or hero attacking the tower itself with auto attack
   
4. Closest enemy creep or hero attacking any friendly unit with auto attack
   
5. Closest enemy creep or hero
   
6. Closest enemy catapult

And these are the "Reseters" (I am hereby defining the following things as "Reseters", and this is how I'll call them throughout the guide, even in the videos), meaning: the tower resets its priority search, if one of the following happens:

• The targeted enemy creep or hero dies
  
• The targeted enemy creep or hero becomes unattackable. (Though "dying" is a special case of "becoming unattackable", I think it is worth stating both conditions separately for clarity).
  
• An enemy creep or hero targets a friendly hero
  
• An enemy hero being attacked by the tower manually attacks an enemy creep or hero (This is the famous tower target switch technique, where you A-attack one of your creeps to "reset the aggro")

Some observations have to be made:

• There is nothing random in the process. It is an algorithm: The tower will recognize the target with the highest priority in the moment, and will attack it to death if no Reseter occurs
  
• Spells ARE NOT AUTO-ATACK. This means you can spam spells under a tower and it won't switch.
  
• Auto-cast spells (like Frost Arrows, Searing Arrows, Arcane Orb), even though are "attacks", count as SPELLS for the tower IF YOU CAST THEM AT THE ENEMY INSTEAD OF USING THROUGH AUTO-CAST AND RIGHT-CLICK. Like before, you can spam them under a tower and it won't switch.
  
• Wards and ward-like spells have the same priority as a catapult. This includes: Plague Wards, Mass Serpent Wards, Nether Ward etc and even movable wards like Healing Ward and Frozen Sigil.
  
• Think about it this way: The tower chooses someone, based on its priority and sticks to it until it dies (a priori). A reseter induces a memory loss on the tower. Then it chooses another unit, based on its priority, and sticks to it until it dies. And so on.
  
• You may have noticed the list is a bit different from the wiki. The wiki's list is wrong, this is the right one. You can test it yourself : ).

Here comes an illustration of the process:

And here comes an example with Drow's arrows:

And if you don't believe this kind of knowledge is useful, here is an application of it in a real game (if Jugg didn't switch the tower's target, he would be dead):

And here is N0tail fountain diving with meepo, where he uses this knowledge:

So, now we have the skeleton. But the skeleton is important, so let's do it one more time, but with another approach.

Illustrative

I'll explain the process in a lucid way now:

I am the tower. I am the almighty tower. There comes some units!

IS SOMEONE ATTACKING MY HEROES NEAR ME?????
Oh, no? Ok...
IS SOMEONE ATTACKING ME????
Oh, no? Ok...
IS SOMEONE ATTACKING SOMEONE THAT I LIKE???
Oh, there is a creep attacking one of my creeps! I'll KILL IT!
Oh, yeah! DEAD!
[Memory Loss]
???? I am the tower. I am the almighty tower. Hey, there are some units nearby!
IS SOMEONE ATTACKING MY HEROES NEAR ME?????
Oh, no? Ok...
IS SOMEONE ATTACKING ME????
Oh, a pesky Sven is attacking me! I'll kill him!
[Sven retreats a bit, in order not to be close to the tower, and A-attack a creep]
[Memory Loss]
???? I am the tower. I am the almighty tower. Hey, there are some units nearby!
(and so on.)

Program-like

Now, if you are familiar with programming, I'll make a pseudo-algorithm to illustrate (mind me, there's a long time I don't play with programming):

if priority 1:
attack target until RESETER, then go back to beginning
else:
if priority 2:
attack target until RESETER, then go back to beginning
else:
if priority 3:
attack target until RESETER, then go back to beginning
else:
if priority 4:
attack target until RESETER, then go back to beginning
else:
if priority 5:
attack target until RESETER, then go back to beginning
else:
if priority 6:
attack target until RESETER, then back to beginning
else:
back to beginning

Tower Range

This section will be rather short, as there is not much to talk about this.

Here are pictures that illustrate the tower range:

Radiant:

http://imgur.com/a/tiQC1#0

Dire:

http://imgur.com/a/UMGYD#0

OBS: The circles show good indicators (like bushes), the lines show the range.
OBS2: Those images were not done by me. They are due to PCGamer. I found it would be rather tiresome and futile to "manufacture" those images when there are very good ones on the internet already.
OBS3: I think the main purpose of these images was not to emphasize on the exact radius, but instead try to create an easy-to-remember scheme (this is all speculation, since, as I said, those images do not belong to me). As such, the pictures do not show the exact radius of towers, and some even have inconsistencies between themselves.

Ways to abuse the knowledge

Well, most people say every knowledge is only as good as its applications. So, let's begin with some strategies:

Tower Diving

The important aspects to remember here are:

• Spells are not Reseters. Abuse this.
  
• Switch targets (A-attack your creeps when they are in a higher-priority state) when you disengage the enemy.
  
• If you have another Hero with you (which is highly advised when you dive a tower), you two can effectively switch the tower's aggro. Notice that some times this will be a two-man job: both of you will have to do your part on changing the aggro.

Illustration of application in tower diving:

OBS: In the video, Tiny could very well have targeted Rhasta. But my intention was to illustrate the possibility of targetting creeps across the map to reset the tower aggro.

Pushing

There is really only one aspect to remember here:

• Switch targets. If you can tank the tower safely for your creeps, do so, switching the tower's aggro to you. If tanking the tower will not be a safe decision, let the creeps do it, and change aggro to them if the tower begins hitting you.

Illustration:

Harassing under tower

Here are the important aspects for this:

• The key to this technique is the difference between Tower Aggro Range (500) and Tower Attack Range (700). Since the Aggro Range is lower, you can try and safely harass an enemy hero under his tower, provided you are not close enough.
  
• A hero usually thinks he is safe from harass under the tower. Exploit this.
  
• Since your creeps are generally close to the hero when you are under his tower, you can try and do a simple but effective psychological game: Attack him under the tower, but away from aggro range. It's possible that he will think the tower will switch to you. If that is the case, he may counter-attack. This will probably cause an entire wave of creeps to turn to him while you are safe.

Illustration:

To see the full power of this technique, watch the following video, where DK.Super! extracts all of its potential against NaVi.Dendi.

Final Remarks

My intention is to keep renewing this guide. If you have any suggestions, please tell me.

TL,DR version of the guide:

If you complain about tower aggro being biased towards you, it's because you are ignorant, not unlucky.




All videos found here were made by me. The "Tower Range" section includes pictures not made by me, but found in PCGamer.

Updates

• 20/07/2014
  - Changed Videos Display
  - Fixed priority list (wiki was wrong)
  - Added Orb-Walking info
  
• 04/08/2014
  - Tower Range section included
  - Added some misc comments in introduction.
  
• 05/08/2014
  - Added information about Ward priority.
  
• 17/08/2014
  - Added Dire towers on Tower Range section.
  - Added info regarding accuracy of the images.
  
• 23/08/2014
  - Added Harassing Under Tower section.

[.]

RUS: Выберите что то одно из этого списка и напишите в моём профиле, отвечу тем же!
ENG: Choose the one that's on the list and write in my profile, I will answer the same!
+rep sf abuse
+rep dead inside
+rep #1 on mid
+rep raze machine
+rep 1000-7
+rep SS+ rank

[casual player)]

Thanks for this knowledge!

[[GZ] schmeling65]

still in Novembre 2016 helfull; thx

[ぜぜぜぇ〜イ！！！]

Could you explain to me in the video where Jugg was hooked by Pudge why he wasnt attacked by the tower while being the closest enemy unit to it?

[HuskUrsa™]

Great job writing this, it helped me a lot

[你跟老子比蠢？]

+

[Grace Bernelli]

@Dest oh yeah didnt think of it like that. It just seemed strange to me when I saw it in the video and felt it out of place since if you have the need to target something far away since no one is close to the towe / you = you are the only one close to the tower = even if you reset the agro the tower re-targets you. If i missed some other use for this far away targeting please do let me know (only thing i can think of is for creep agro to go for you when no heroes are nearby and u want to spin with axe ;p) Other than that great guide since newer players really often seem to think that it is indeed random how the towers work. Had hard time proving that it wasnt random... I checked the wiki and according to that the range for towers is 700 which indeed would make the pictures not correct like you stated, since it should be a circle but for newer players those pictures are perfect since its more important for them to simply stay safe :) good job man !

[Sasukekw Uchihaha]

@Grace Bernelli You are right, but that was intended to illustrate the fact that you can target things that are far away. As you can see, it is explicitly stated that a reset occurs when "An enemy hero being attacked by the tower manually attacks an enemy creep OR HERO". Nevertheless, I think that your observation is valid for educational purposes. Adding an observation below the video. Thanks

[Grace Bernelli]

Oh and btw you dont even have to go test that since one of the other videos u linked ( the one with notail meepo) shows this. He simply clicks on his other meepos which counts as other heroes. On the tiny rhasta video the tiny could've simply clicked on rhasta for the agro to change.

[Grace Bernelli]

on the video where tiny and rhasta killed lion under tower. He looks far away for a creep for the tower agro reset. As far as i know u can do the same by doing the click on a hero no need to search far away for creeps like done in the video.