Question as to the Eth bug

[BugBoy]

That Eth grants ITD is a well-known fact. However, I'm wondering about some slightly more obsecure bits of info.
Firstly, the Eth rune grants reduce-ac in weapons. -25 reduce-ac to be exact.

Now, what I'm first wondering is, does Eth cause auto-hit? That is, if you were extremely low level and attacking a very high level target, while using Eth, will you still hit 95% of the time?

Secondly, I've heard that Eth reduces target's def to a negative number. Does anyone know if this is true? I seem to recall that with a 1.08 Arreat's Face, it had reduce-ac with a value of 10, and it reduced the target's AC to 10% of what it would be normally. If true, and the reduce-ac on Eth works the same way now it would imply that if a target has 100 def normally, it would have -25 def with Eth.

If so, is the negative number used for the purposes of the to-hit calculation?

I searched, but was unable to find any information.

[Tycho Maudd]

Your to-hit cannot go above 95%; and yes, eth causes your target to have -def during the to-hit calculation basicly negating AR.

[Ruvanal]

The effect of Eth is outlined in this thread.

http://www.theamazonbasin.com/d2/forums/in...ST&f=35&t=27393

[HunkyDory]

I repost my original posts here:

First of all I would like to point out that Ruvanal supplied most of the information and that Adeyke had a role in it too :

Below a snippet from the WitchWild guide.


The bows mentioned in this snippet are for comparison only.
Please no which is better discussion. :D

CHANCE TO HIT
Chance to Hit determines if you hit a monster succesfully and is only used to determine this chance when you use a non autohit Bowskill.

Non-autohit Amazon Bowskills :
Magic Arrow
Multishot
Strafe

This implies that if you use any of the above three skills on a regular base Chance to Hit is something you might want to know more about.
If you do not use any of them then I advise you to read this section for future reference.

Chance to Hit is capped at 95% chance and is calculated as follows :

200 * (AR / (AR + DR)) * (AL / (AL + DL))

AR is Attacker's Attack Rating
AL is Attacker's Level
DR is Defender's Defense Rating
DL is Defender's Level

Attack Rating is calculated as follows :

(((Dexterity * 4) - ToHitF) + Sum of +X to AR items) * (1 + ((Sum of +% to AR items + percentage of Penetrate Skill) / 100))

For an Amazon ToHitF is 23.

ToHitF (1) is calculated as follows :

28 - ToHitFactor class

ToHitFactor class :
+5 Amazon
-15 Sorceress
-10 Necromancer
+20 Paladin
+20 Barbarian
+5 Druid
+15 Assassin

Example:
If you have 400 Dexterity, wear a Ravenfrost ring with 211 to AR and a item with +20% to AR bonus and Penetrate Skill with 110% your Attack Rating would be :

(((400 * 4) - 23) + 211) * (1 + (130 / 100)) = 4112

Note :
The Paladin skill Fanatism and the Druid skill Heart of Wolverine will increase your Attack Rating if you are partied with such a Paladin and / or Druid and you are in effective range of said skills.

Examples to clarify Chance to Hit Formula :
Attacker's Dexterity : as much as needed to get a 95% Chance to Hit
Attacker's +AR items : 23
Attacker's Penetrate Skill : 0
Attacker's Attack Rating : depends on amount of Attacker's Dexterity
Defender's Defense Rating : 500 (Cows on Hell have 500ish DR)
Defender's Level : 90

Attacker's Level 70 :
Dexterity is 12375
Attack Rating is ((12375 - 23) + 23) * 4 = 49,500
200 * (49,500 / (49,500 + 500)) * (70 / (70 + 90))
49,500 / (49,500 + 500) = 49,500 / 50,000 = 0.99
70 / (70 + 90) = 70 / 160 = 0.43
200 * 0.99 * 0.43 = 85% Chance to Hit

Attacker's Level 80 :
Dexterity is 12,375
Attack Rating is ((12,375 - 23) + 23) * 4 = 49,500
200 * (49,500 / (49,500 + 500)) * (80 / (80 + 90))
49,500 / (49,500 + 500) = 49,500 / 50,000 = 0.99
80 / (80 + 90) = 80 / 170 = 0.47
200 * 0.99 * 0.47 = 93% Chance to Hit

Attacker's Level 90 :
Dexterity is 2375
Attack Rating is ((2375 - 23) + 23) * 4 = 9500
200 * ((9500 / (9500 + 500)) * (90 / (90 + 90))
9500 / (9500 + 500) = 9500 / 10,000 = 0.95
90 / (90 + 90) = 90 / 180 = 0.50
200 * 0.95 * 0.50 = 95% Chance to Hit

Attacker's Level 99 :
Dexterity is 1438
Attack Rating is ((1438 - 23) + 23) * 4 = 5752
200 * (5752 / (5752 + 500)) * (99 / (99 + 90))
5752 / (5752 + 500) = 5752 / 6252 = 0.92
99 / (99 + 90) = 99 / 189 = 0.52
200 * 0.92 * 0.52 = 95% Chance to Hit

As you can see from the above examples the difference between the level from the Attacker and the Defender has the greatest impact on the formula. It effectively chokes the Chance to Hit from increasing when the Attacker's level is below that of the Defender's Level.

The amount of Dexterity from the above examples is not realistic hence a more realistic example :

Attacker's Level 90
Attacker's Dexterity is 300
Attacker's +Ar items : 208 ie. 1 Ravenfrost Unique ring could supply this amount
Attacker's bonus from Penetrate skill : 225% (level 20)
Attack Rating is (((450 * 4) - 23) + 208) * (1 + (225 / 100)) = 4500
200 * (4500 / (4500 + 500)) * (90 / (90 + 90))
4500 / (4500 + 500) = 4500 / 5000 = 0.90
90 / (90 + 90) = 90 / 180 = 0.50
200 * 0.90 * 0.50 = 90% Chance to Hit

It is reasonable to assume that trying to reach a 90% Chance to Hit (1 in 10 attacks will miss) is better than a 80% Chance to Hit (1 in 5 attacks will miss).
After 90% it will not make much difference though it may look nice on your screen to have a 95% Chance to Hit.

The effect of Chance to Hit is much bigger than it may look at first sight.

Some musings to illustrate this effect with a 75% Chance to Hit (1 in 4 arrows will miss)

Chance to Hit : 75%
Defender's Life : 300
Attacker's Damage : 100
Attacker attacks with Multishot (ignore the -75% penalty of MS)

Attacker will need to attack 4 times to be sure (on average) that the Defender is killed. It takes 3 hits to kill the Defender.
The Worst Case scenario is when the third hit happens on the fourth Attack :
Attack 1 : Miss = Defender Life 300
Attack 2 : Hit = Defender Life 200
Attack 3 : Hit = Defender Life 100
Attack 4 : Hit = Defender Life 0 means Defender is Killed.

Now we can take a look at Bow / Crossbow speeds and the impact of the above.
Remember we are still talking about the average chance that this will happen, it is not a certainty that it will happen.

Bow speed 9 frames
Attack 1 : 9 frames
Attack 2 : 18 frames
Attack 3 : 27 frames
Attack 4 : 36 frames

Crossbow speed 13 frames
Attack 1 : 13 frames
Attack 2 : 26 frames
Attack 3 : 39 frames
Attack 4 : 52 frames

Compared to the 36 frames from the Bow the Crossbow took 52 frames or 44% more frames than the bow with the same Chance to Hit.

If we raise the Chance to Hit to 90% both the Bow and the Crossbow will probably kill the Defender within the first three attacks.

Compared to the 27 frames from the Bow the Crossbow took 39 frames or 44% more frames than the bow with the same Chance to Hit.

That is why the slower the attack speed the more important the Chance to Hit becomes.

The only way that the Crossbow can compete with the Bow is when it has a higher damage and kills the Defender with less hits and / or has a higher Chance to Hit than the Bow. Though the latter will become less important when both Bow and Crossbow approaches or have a Chance to Hit of 90%.

Defender killed with 2 hits damage is 150
Chance to Hit is 90% (1 in 10 arrows miss)
Attack 1 : Hit = Defender Life 150
Attack 2 : Hit = Defender Life 0 means Defender is Killed.
Attack 3 : irrelevant
Attack 4 : irrelevant
It took 26 frames to kill the Defender with the Crossbow, with the Bow it takes 27 frames (3 * 9)
Damage from the Crossbow has to be 50% higher than that of the Bow to be equal in Killing Speed when both have the same Chance to Hit.

Defender killed with 1 hit damage is 300
Chance to Hit is 90% (1 in 10 arrows miss)
Attack 1 : Hit = Defender Life 0 means Defender is Killed.
Attack 2 : irrelevant
Attack 3 : irrelevant
Attack 4 : irrelevant
It took 13 frames to kill the Defender with the Crossbow, with the Bow it takes 27 frames (3 * 9)
Damage from the Crossbow has to be 300% higher than that of the Bow to be faster in Killing Speed when both have the same Chance to Hit.

The above is not exact science but gives an indication of how the process works.

Now we can compare the WitchWild string to a certain popular Crossbow :

170% WitchWild String with a character at level 99
Average Damage is 60
Deadly Strike is 99%
Average Damage is 60 * (1 + (99 / 100) = 119
WitchWild String speed 7 / 8 / 9 / 10 frames
Attack 1 : 7 / 8 / 9 / 10 frames damage is 119
Attack 2 : 14 / 16 / 18 / 20 frames damage is 238
Attack 3 : 21 / 24 / 27 / 30 frames damage is 357
Attack 4 : 28 / 32 / 36 / 49 frames damage is 476

200% certain Crossbow with a character at level 99
Average Damage is 258
Critical Strike is 68%
Average Damage is 258 * (1 + (68 / 100) = 433
Certain Crossbow speed 13 frames
Attack 1 : 13 frames damage is 433
Attack 2 : 26 framesdamage is 866
Attack 3 : 39 frames damage is 1299
Attack 4 : 52 framesdamage is 1732

If we look at the tables we can see that by the time the Certain Crossbow has fired two attacks (26 frames) the Witchwild String has fired three attacks (27 frames with 9 frame speed).

The Certain Crossbow does with two attacks 433 * 2 = 866 damage and takes 26 frames for that.
The WitchWild String at 9 frames speed does with three attacks 119 * 3 = 357 damage and takes 27 frames for that.
Compared to the WitchWild String the Certain Crossbow does 142% more damage.
If we compare just the bow damage than the Certain Crossbow does 330% more damage than the WitchWild String.
Notice that the 99% Chance on Deadly Strike that the WitchWild String has makes up a for a lot of damage.

For completeness sake let us compare a 300% Cruel Matriarchal Bow with 7 / 8 / 9 / 10 frames speed to a Certain Crossbow with 13 frames speed.

300% Cruel Matriarchal Bow with a character at level 99
Average Damage is 33.5 (1 + (300 / 100)) = 134
Critical Strike is 68%
Average Damage is 134 * (1 + (68 / 100) = 225
300% Cruel Matriarchal Bow speed 7 / 8 / 9 / 10 frames
Attack 1 : 7 / 8 / 9 / 10 frames damage is 225
Attack 2 : 14 / 16 / 18 / 20 frames damage is 450
Attack 3 : 21 / 24 / 27 / 30 frames damage is 675
Attack 4 : 28 / 32 / 36 / 40 frames damage is 900

The Certain Crossbow does with two attacks 433 * 2 = 866 damage and takes 26 frames for that.
The WitchWild String at 9 frames speed does with three attacks 119 * 3 = 357 damage and takes 27 frames for that.
The Cruel Matriarchal at 7 / 8 / 9 / 10 frames speed does with three attacks 225 * 3 = 675 damage and takes 21 / 24 / 27 / 30 frames for that.

Compared to the WitchWild String the Certain Crossbow does 142% more
damage.
Compared to the Cruel Matriarchal the Certain Crossbow does 28% more
damage.
Compared to the WitchWild String the Cruel Matriarchal does 89% more
damage.

If we compare just the bow damage and nothing else than :
The Certain Crossbow does 330% more damage than the WitchWild String.
The Certain Crossbow does 92% more damage than the Cruel Matriarchal.
The Cruel Matriarchal does 123% more damage than the WitchWild String.

From this we can conclude that both speed and Chance to do Double Damage have a great impact on the final damage.

Remember that both the WitchWild String and the Cruel Matriarchal will have more dexterity available to its owner due to the lower strength requirements when compared to the Certain Crossbow.
For the WitchWild String that can be as high as 45 dexterity
For the Cruel Matriarchal that can be as high as 23 dexterity.

I did not take that extra dexterity into account to avoid making the calculations more complex than needed.

Remember that the faster bows will benefit more from your elemental damage as they attack more often than slower bows / crossbows.

The above applies to Strafe as well though Strafe works much different than Multishot due to the length of the Strafe cycle which can vary from 1 - 4 to 10 arrows. Each arrow from the cycle is treated as a seperate attack.

Note : Only Physical Average Damage was compared in all of the above examples nothing else.

Conclusions :

Chance to Hit is important, try to aim at 90% Chance to Hit at character level 90.
More is nice but not mandatory.
Defender Level is the most important factor that influences Chance to Hit. If your level is lower than the Defender's Level there is not much you can do to better your Chance to Hit.
With a faster bow you can afford to miss more than with a slower bow/crossbow.
The slower the bow the higher the damage has to be, to equal or better a faster bow.
The faster the bow the more it will profit from elemental damage and the more likelier that chance based effects will happen.

(1) as always this data has been provided by Ruvanal

[HunkyDory]

Concerning the Eth bug :

Attacker's Level 70 :
Dexterity is 62
Defender's Defense does not matter, it will be set to zero by Eth bug.
We use 500 as an example.

Attack Rating is (62 * 4) - 23 + 23 = 248
Defense Rating is (500 * -25) / 100 = -125

The following is used only when either Attack Rating and/or Defense Rating ends up with a negative value ie. a sanity check is done.
Attack Rating is 248 + 125 = 373
Defense Rating is -125 + 125 = 0

Now the game will calculate the Chance to Hit as usual :
200 * 373 / ( 373 + 0) * 70 / ( 70 + 90)
373 / (373 + 0) = 373 / 373 = 1
70 / (70 + 90) = 70 / 160 = 0.43
200 * 1 * 0.43 = 86% Chance to Hit

A Chance to Hit of 86% at level 70 can be considered as Ignore Target Defense.

The nastiness is in the fact that Defense Rating ends up as zero which will always set the second term used in the Chance to Hit formula to 1.
This will break the formula.

But I consider this a very nasty bug and not done.

I will not put the above in the Guide.

Regards, Hunky

edit: reworked the example after Ruvanal pointed out how it really works.
My gratitude goes to him for being the Eternal Flowing Fountain of Knowledge.