Firewall Guide


Basic Information

° Magic needed to cast from Staff: 27, from Scroll: 17,

from memory: 28 mana and decreases by 2 mana every Slvl.

° Magic needed to learn Slvl 1: 27, Slvl 2:32, Slvl 3:38

° Duration: 8 + 8 x Slvl seconds - Slvl 1 Firewall will last 16 seconds and 8 seconds

more for each Slvl.

Note: There is a difference between Slvl 0 and Slvl1 Firewall. Firewall cast from staff or scrolls when you don’t know the spell is counted as Slvl 0, which means it will only last 8 seconds.

° Number of flames: 12 per cast and uses up 12 sprites(this number will have some significance later on) The central fire wall flame actually consists of two flames on top of each other, with the result of a damage for that "flame" being double.

° The flame will try to hit once every 0.05 seconds for a total of 160 + 160 x Slvl times - meaning 20 times per second for the duration.

It’s interesting to note that Firewall damage is not directly controlled by Slvl but Clvl. So, even if your Slvl stays the same your Firewall will do more damage per hit as you gain Clvl. If the monsters can be convinced to stay in the Firewall, they accumulate damage for the duration of the Firewall, which is calculated by Slvl.
Note: Firewall will always check for ToHit%

Also note that the listed damage in your spell book is not the same as the real damage your Firewall can do.
Listed Damage: Min Dmg: 4 + 2 x Clvl. - Max Dmg: 40 + 2 x Clvl
Real Damage: (rnd[10] + rnd[10] + Clvl + 2) / 8

Example: Avg of rnd[10] is 5.5 @ Clvl 6 * 20 times/second. (5.5+5.5+6+2)/8 = 47.5/sec

More Examples:


Listed Avg Dmg

Real Avg Dmg

Clvl 6:

16-52 = 34


Clvl 12:

28-64 = 46


Clvl 18:

40-76 = 58


Clvl 24:

52-88 = 70


The good news is Firewall does a lot more damage than it’s listed on your spell book!


First, a clarification about Diablo’s coordinate system. In Diablo, the coordinates are tilted 45 degrees to the right (clockwise) on your screen just as the auto-map is. The four blue lines in the picture below represent the true X and Y axes as well as the directions (E)ast and (S)outh. In this article, when I refer to a Straight cast it means the cast is perpendicular to the Blue axes, and a Diagonal cast is perpendicular to the red lines. The Firewall you see at the bottom is considered as a Straight cast, for example. In case you are wondering what all the other elements in the picture are for you’ll just have to wait, we’ll come back to it later.


Basic Casting Instructions

We all know that a straight cast is better than a diagonal cast (right?). When monsters are walking toward you through a diagonal Firewall, there is a good chance they will not be damaged at all due to one of Firewall’s bugs. Yes, it’s a bug. The evidence is more convincing when casting a Flamewave diagonally - every other tiles will be missed by the wave. Besides, you can see from the pic below that a diagonal cast does not give much of a coverage. So how do you avoid a bad cast? As a rule of thumb, your cursor should not highlite any monster when casting, especially in a coop situation. The monster may move and your Firewall targeting will move with it. That is the reason why so many Firewalls are miscast when you can swear your aim was right on. The pic on the left shows such a cast.

If the cursor was just a few pixels to the right it would have highlited the other toady and you would fry your partner too. In general, it’s better if you stand off to the side in opposite direction of the traffic flow as in the pics. Draw a mental line formed by the toadies (where you expect the monsters to line up) and another line from yourself to the South (in this case) as indicated by the blue line. Where the two lines intersect, shown by the rejuv potion on the left pic and the cursor on the right pic, is your targeting for a perfect straight cast.

If you have problem imagining a perpendicular line from you to where you want to cast the Firewall, or because it’s too dark to see clearly, try to stay close to a wall and run you cursor along the wall. 

Bonus Tip
: After the area is established and set as the killing zone, drop a potion or 1 gold piece on the ground where you would aim to cast. Now all you have to do is aim at the potion or gold piece, can’t get easier than that. This tip works great especially in the Caves when the team is set behind a fence. The tricky part about fences is that the fence posts are too narrow to take up a whole tile making it hard to judge accurately if you are pointing at the tile that is part of the fence or not. Or, you maybe standing too far behind so it’s too dark to see clearly. A split second delay in making a decision can often result in total disaster when you are in the caves, so just hop over the fence and place a lousy gold piece there.



Doors - Light My Fire

Now, you come upon a door into a new room and you are sweating beads. This is where you usually test you partner’s reaction time by setting a Firewall on him, right? You have heard people tell you”cast on the step”. You have heard people say “point just inside the room”, you have heard... never mind, you are getting inconsistent results and still casting Firewalls on the wrong side of the wall.

So what’s the deal?

Actually, both ways of targeting are correct. You just have to know which one to use, and when. You see, Diablo is full of wonderful little bugs. This particular bug that killed many an Ironman has something to do with directions, more precisely, which side of the door the caster is on.


The first pic suggests casting on the step and it would work every time IF you are facing West (and South). 

The second pic suggests casting just inside the step IF you are facing North (and East). If you were to cast on the step when facing North and East, the Firewall will be laid on your side of the room and B-B-Q your partners guarding the door. Trust me on this one! You can still cast a Firewall inside the other room (by targeting the step) when you are facing North and East, if you stand right up against the door. Since you can’t cast Firewall on yourself, it will be forced to go over the wall.

So why not just cast inside the room all the time?
This take us back to the Basic Casting Instructions at the beginning - Most likely, there are monsters right at the door that will misguide your targeting. Ironman cannot afford to waste resources if they can help it. So how do you avoid casting diagonals when you have to point inside the room and highlite a monster? We will come back to this later in the Margin for Errors section. Lets look at some ways to use Firewall for now.




First of all, do not use Firewall just because you can. You need to conserve resources and use it when it counts:

(1) A roomful of monsters, your Firewall can kill tons of monsters instead of a few.

(2) The monster mix is too much for your partner(s) to handle. Besides, if you overkill, your warrior may become too weak due to the lack of exp points. A weak warrior can’t hold the monsters at the Firewall.It is very inefficient to cast Firewalls hoping the monsters will walk through them to get to you. They will only get hit once or twice and sometimes not at all. The idea is to cast Firewalls just in front of the warrior (or whoever the shield happens to be at that time. Yourself if solo), the monsters will line up to take in the full damaging effect - 20 times a second for the duration of the spell. Have Heal Other readied after the FW is set, look after your “Shield” and make sure he’s in good health.

Casting into a room with door is one of the most frequently used techniques.

One method is to have the “Shield” open and plug the door while the mage cast a Firewall on the first row of tiles inside the room. This is a good formation to use when you expect range attackers, and especially when mage has no Mana Shield. 
Another variation, the mage shotgun with warrior and rogue on each side of the door, is to have the mage open the door, and close the door after the cast if necessary. This method works great when the monsters are too tough for the warrior to handle, as well as facing off with Black Deaths. The Mage-Shotgun also has the advantage of plugging the door so no “liquid” monsters can sneak pass the door and create chaos.

When approaching a room with an open arch - Warrior peek around the corner, hugging the outside wall Cat walk, making sure it’s safe for the mage to advance just around the corner to cast a Firewall. This time the FW cuts into the room with the warrior standing by the column to hold off the horde. After the first wave of monsters, the warrior will then go up and down along the Firewall inviting more monsters to the roast.


Laz’ Chamber need not be feared if you know where the monsters are.

The pic shows where everyone is when undisturbed. Note that there are always 4 doormen in Laz’s chamber and the first one on the right is on the first row immediately inside the chamber, second one on the right is on the third row. The first one on the left is on the second row, and the second one on the left is on the fourth row. 

You can approach the chamber opening from as far South as the layout allows, then stop at 3 tiles away without activating anyone. Now, just lay four rows of Firewalls inside the room where the Advocates are. Listen for the sound of Advocates roasting and dying, recast if necessary. Although I would not recommend it (there are better ways to activate them one at a time), you can also fry and activate the 2 unique witches while the Advocs are roasting. Still standing at the same spot, you can see the top of the cool design (four pointed star) on the extremely top left-hand corner of your screen. Casting a Firewall there will activate both witches.


The preferred spot to kill Diablo is at one of the corner of the two-lever room

That corner spot offers many advantages, 3 of them being:

(1) It’s easier to control where Diablo will stand.

(2) Player(s) don’t get knocked back and therefore keeps Diablo in the fire.

(3) Mage (and the rogue) standing around the corner will not be attacked by Diablo’s Apoc.

When the warrior and Diablo is set at the corner, the mage can cast the Firewalls on big ugly and still out of his line of sight and attacks. The mage and rogue can now move into the sniper position to give the warrior a hand. 
Another big advantage of using the corner is that you can stack more Firewalls than the normal sprite limit would allow.

Normally, this translate to 10 Firewalls to be cast (12 flames x 10 = 120, close enough). 
But not every Firewall uses up 12 flames/spirit, when casting around the corner it will only allow 9 flames for each Firewall so you can stack almost 14 Firewalls. And. if the party feel confident enough to have the mage standing next to the warrior at the corner, the flame count per Firewall would go down to 7 letting you stack the Firewalls 18 deep - that’s virtually doubling the damage or half the time needed to kill when comparing to a full spread Firewall. This may sound obvious but for the sake of those who doesn’t know already - stacking Firewalls (placing FWs on the same spot) multiplies the damage done by the amount of Firewalls stacked.



Bonus Tips - Hidden AI


So you are a low level character with low Slvl Firewall (in comparison to the Mlvl).

You see a room full of Hidden type monsters and cast a Firewall in front of you. You have just wasted some precious mana because your Firewall is not doing enough damage. The Hiddens run away from the stun and your Firewall is (almost) dead by the time they return. You can waste more mana and repeat a few times or you can exploit the Hidden AI. Cast another Firewall behind them to cut off their escape route as seen in the picture. The Hiddens don’t even have a chance to ping pong back and forth the Firewalls; they will be locked in perpetual stun until they die.

Margin for Errors

I forgot to mention that you can only cast Firewall in 8 directions, but you probably know this already.
So, unless you cast exactly in any of the 8 directions, the game would have to decide for you which of the 8 directions to lay the Firewall. Take a close look at the picture beyond.

Note that the potions are laid out in eight distinct directions radiated from the caster.

What this shows, graphically, is the margin for errors - how the game decides which direction your Firewall should face. In other words, if your cursor is within the piles of red potions, your Firewall will be cast diagonally. Likewise, if you place the cursor within the piles of blue or yellow potions, you’ll have a straight Firewall.


The faint blue lines eastward are there to help demonstrate an interesting point. The diagonal patterns in which the margins (potions) expand outward from the caster are not the same as the straight patterns. The diagonals take on a saw-tooth pattern while the straights take on a step like pattern. This behavior requires you to be quite accurate when you want to cast a straight Firewall at close range - there is no margin for error, relatively speaking.


Which takes us back to “So how do you avoid casting diagonals when you have to target inside the room (or anywhere for that matter) and highlite a monster?”  


Simple, stand as far back from the door as possible and have your partner open the door. The further you are from the target, the greater the margin for errors you’ll have.

And, you can even stand off to the side if the situation requires. You are probably thinking no way I can cast a Firewall into that room, and a straight one at that - I was clearly standing at a 45 degree angle from the door! Well, this only works when you are casting over a wall.

Which in turn takes us to another point of interest - Line of Sight (LoS), and possibly another program irregularity.



Line of Sight

First, a couple pictures of the same room to demonstrate what is and isn’t considered LoS. The first picture with the caster standing to the right has LoS, you can draw a straight line from the caster through the door into the room. So, Firewalls can be cast inside the room. 


The second picture with the caster standing to the left of the same room does not have LoS. Apparently, you need to see at least a full tile before it’s considered LoS. 


Angle = From the caster to the door to the cursor.
As long as you have LOS into the room (not the same as just being able to see what’s over the wall), Firewalls are cast as if you were standing centered to the door (with some *adjustments*).

Casting behind a wall corrects your angle of casts
. Even when casting at an acute angle your Firewalls will be straight if the angle, bends toward the side of the door you are standing on.


Adjustment differs slightly from room to room. It may works to your advantage when you just want a Firewall up against the wall, because you can be off by 2-3 tiles further inward. Generally, you’ll need to place your cursor 2 rows further than the row you want the Firewall to be on, if you are 2 tiles off to the side, and 3 rows further if 3 tiles off to the side etc. Also note that the center of the first Firewall is shifted to the left, and more so on the second Firewall.

Warning: Don’t try this in an Ironman game without practice.
I do not recommend standing too far off to the side (as shown in the picture) as it requires a lot of practices to get consistent results. For example, you’ll get better results when you are no further than 2 tiles off to the side if you are 4 tiles away from the door.





Firewall bug explained
First a pop quiz - What is different in the two pictures below? What is the significance?

The map as we now know is tilted 45 degrees clockwise and the game uses this system. In other words, walking up/downward on the screen is walking diagonally.


The illustration shows walking up/down is walking diagonally according to the game.

To prove this, I will also clear up one common misunderstanding when people claim if you walk diagonally across a Firewall you don't get hurt. This is only true in one condition, also the answer to the pop quiz. Pretend the yellow colored tiles is a Firewall. The warrior in the picture will get hit if he walks downward. But wait, since the game treats SW to NE as diagonal that would mean...

If the warrior's original location was 1,0 and walks downward, his steps will be 1,0 to 2,1 to 3,2 - the yellow line. No wonder he doesn't get hit. (That, btw, is the answer to the pop quiz.

You can walk downward across the Firewall without getting hurt in the first picture)

That is the only way to walk across a Firewall without getting hurt, not "diagonally" as misunderstood. If the Firewall is laid along the X or Y axes, you will get hurt no matter how you walk across it because you would have to step into a flamed tile.

This also explains why Flamewave would miss every other tiles when cast diagonally. 

There’s yet another game abnormality that will allow one to walk across the Firewall without getting hurt. Player walking left to right and vice versa, from 0,4 to 4,0 for example, are immune to attacks ranged attacks and spells and not just Firewall either. Indeed, one can walk across a roomful of Firewalls without a hit.




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