OK… so what is “threat”? Threat is a measurement of just how much the mob dislikes someone. A tanks job is to generate the maximum possible threat; everyone else’s job is to maximize damage while keeping under the tank’s threat value.
It’s not an incredibly simple subject, and it’s taken about a year and a half for the community to solidly figure out how exactly threat works.
*note* — In 1.12, everything was changed to be multiplicative. This means that defensive stance, bear form, defiance and feral instinct are more effective now than they were previously; while threat reducing abilities and stances are less effective. It’s probably a wash all in all, but it makes some of the numbers below inaccurate. I’ll update them eventually. 
The Basics of Threat
Before any modifiers, 100 points of damage = 100 points of threat. 100 points of healing = 50 points of threat. (overheals do not count; only actual health restored)
Rogues have an innate 20% base threat decrease. 100 points of damage = 80 points of threat
Warriors in Battle and Berserker stance have a 20% base threat decrease. 100 points of damage = 80 points of threat.
Warriors in Defensive Stance have a 30% base threat increase. 100 points of damage = 130 points of threat.
Druids in Bear form have a 30% base threat increase. 100 points of damage = 130 points of threat.
Druids in other forms have no innate threat modifiers. Yes, this includes cat. Yes, that sucks and they should get the same reduction rogues get. Hell yeah! Druids in cat get 20% base threat decrease now. 100 points of damage = 80 points of threat as of 1.12.
Paladin healing spells generate half the threat of other heals. 100 points of healing = 25 points of threat.
Mages, Priests, Warlocks, Hunters, and Shaman have no innate threat modifiers.
I’ve seen suggestions in the past that some schools of magic produce more or less threat than others (something like shadow > fire > nature > frost > arcane > holy in order of highest to lowest) but I’ve never seen any substantive testing on it, I’m just including it here in case someone mentions it.
Talents and Buffs
Several classes have talents in their talent trees which allow them to reduce overall threat or reduce threat for specific activities. I’ll take one example, the druid healing talent, Subtlety. Subtlety grants a 20% reduction in threat for all healing spells. So 100 points healed = 40 points of threat.
The Tranquil Air totem and Blessing of Salvation skills reduce threat by 20% and 30%, respectively. These reductions are applied after any innate and talent-based modifiers (so for example, an alliance druid with 5/5 subtlety and Blessing of Salvation will generate 28 threat for 100 points healed, not 25.)
“Stealing Aggro”
Making a mob decide it hates you badly enough to leave its current target and go after you isn’t as easy as you might think. Just being higher on the hate list won’t do it. You have to be *enough* higher. How much is enough? That depends on where you’re standing.
Apparently, mobs are lazy and do not like to move. If you are in melee range of the mob, you need exceed its current target by only 10% + 1 point of threat, and the mob will happily decide he hates you best, at which point, he will not leave you until someone else generates 10% + 1 point more threat than you now have.
At range, you have to work a little harder. It takes 30% + 1 point more threat to pull aggro from outside melee range. Fortunately, someone in melee range can still take it back by generating 10% + 1 point more than that 30% + 1 that stole it.
Taunting
And that’s where taunt comes in. Druids in bear and warriors both have functionally the same taunt; the druid’s is a bit better because it has a shorter cooldown and costs no rage. (that was a stupid statement I didn’t research first, sorry)
Taunt has basically two effects:
A taunted mob is forced to attack the taunter for a few seconds
The taunter’s threat is increased until it is *equal* to the previous target. (note: there is some debate on this. It may be that threat is increased to the *highest* person on the mob’s threat list, even if the mob currently has the tank targeted. This would be useful, but play it safe and assume it’s the less useful version)
So, as noted above, the taunter has those few seconds to generate enough threat to be 10% + 1 above the prior target.
Producing Threat
Fortunately, there are a number of moves in the game which generate greater threat than their damage would indicate. As I noted in an earlier part of the site, Hunters have a ranged skill called Distracting Shot which generates a good chunk of threat. The bulk of threat generation is centered in the tanking classes — the Warrior in Defensive Stance and the Druid in Bear Form.
While both of these generate significant threat, they do it in a very different manner. In brief, for a druid, most of the druid’s damage is multiplied by a base number to create threat; so the amount of damage a druid can do greatly affects his ability to build threat. A Warrior, on the other hand, gets the majority of his threat from static values added to his various skills; the damage those moves may do generates no more threat than his regular autoattack (though his damage certainly makes a difference in his ability to hold threat, it’s not nearly as central to the experience as the druid’s).
For simplicity’s sake, the following numbers assume that the druid and warrior are both specced for tanking, with 5/5 points in their respective threat increase talents.
Druids first, because they’re simpler — a druid has only a few moves in bear form. Fortunately, that’s all he needs:
Maul generates 2.54 x damage in threat. So a 1000 point Maul is 2540 points of threat.
Swipe generates 2.54 x damage in threat. So a 100 point Swipe is 254 points of threat on up to 3 targets.
(2.54 is calculated as follows: 30% threat increase from Bear form, 15% increase from Feral Instinct, Maul/Swipe generate 1.75x damage in threat prior to other modifiers)
Faerie Fire generates 157 points of threat. Not alot, but it’s rage-free on a 6 second cooldown and reduces the mob’s armor, making your Maul and Swipe more effective
Demoralizing Roar generates 58 points of threat on all mobs in range. Pretty insignificant, but you might be surprised how much it cuts down on the damage mobs deal, particularly hard-hitting bosses. It’s very different than how it works on other players.
Bash… I haven’t seen any information on how much threat bash does, but everything in MC except maybe a few of the boss adds are imune to it anyway. Ditto for Feral Charge (though I use that extensively in BWL).
Warriors have a larger pool of talents to play with:
Sunder Armor: 379
Heroic Strike*: 211
Revenge*: 457
Shield Bash*: 261
Shield Slam*: 363
Thunder Clap*: 189
Demo Shout: 63
Each move listed above generates threat equivalent to the amount of melee damage listed next to it. The ones which are marked with asterisks also do damage, which is multiplied by the defensive stance modifier and added to the total
It should be noted that damage shields also benefit from the increased threat from defensive stance and bear form. Always thorn the tank, and if you have a spare pally, it might not hurt to have retribution aura on along with devotion.
Shedding Threat
Some classes have ways to shed threat, either permanently or temporarily:
A Rogue can Feint, which reduces threat on a single target (at the max rank of the spell, found as a drop in AQ20) by 800; equivalent to 1000 damage from a rogue. A rogue can also Vanish, which wipes their aggro completely and returns them to stealth.
A Druid in cat form can Cower, whch reduces threat on a single target by 600, equivalent to 600 damage from the druid.
A Hunter can Disengage (allegedly. I don’t think i’ve ever seen one actually do it), which reduces threat on a single target by 405. They can also Feign Death, which wipes aggro completely and puts them out of combat.
Priests have a skill called fade, which reduces temporarily reduces their threat by 820 to all targets. One of the Tier 2 set bonuses is called “reactive fade” and will often automatically cast a free fade for the priest if he’s taking damage. Fade is only temporary though; the threat returns after the buff ends.
As of 1.12, if a player has BoS or Tranquil Air Totem, it will reduce the threat reduction of Feint, Cower, Disengage, and Fade by the same percentage that it reduces threat from other moves, making threat shedding less effective.
Frost Mages, Paladins, and Warlocks have temporary invulnerability skills (and there are a couple of potions that function similiarly) which reduce their threat values to 0 and make them invincible for the duration of the spell. Paladins can cast a weaker version of theirs, called Blessing of Protection, on other players, making them invulnerable to physical damage only. I’m not 100% sure if this reduces their threat to 0 on everything or just melee targets. They can also cast Divine Intervention, which kills the pally in order to put the target inside a totally invulnerable shield for several minutes, taking them completely out of combat. This is mostly used for wipe prevention. And humor. :-). Except for Divine Intervention, though, when these buffs wear off, the player regains 100% of their original threat.
Dying and being ressed wipes all threat. But I don’t recommend that one much.
Although I don’t know for certain about Blessing of Protection, I can tell you absolutely that a Limited Invulnerability Potion does not reduce threat to zero against mobs that have magical attacks.
You see, I was running 45-minute Baron, and in my infinite wisdom I thought I (a mage) would just go trinket and timer happy and AoE Nuke the skeletal blackguards. Now, I had a stack of Limited Invulnerability Potions on me, and when I dropped to about 20% health I drank one. In this case it permanently lowered my threat to zero, as I was promptly killed by 6 simultaneous Shadow Shock spells.
I expect Blessing of Protection would’ve had the same threat effect, as its physical immunity is identical.
Comment by Zarakaar — June 14, 2006 @ 7:07 am
Paladin healing spells are 33% aggro, not 50% like everyone else.
Seal/Judgement of Light/Wisdom are both the regular 50% aggro.
Comment by Sabin — June 19, 2006 @ 11:06 am
I’ve seen that before Sabin. Do you have any links for confirmation with tests and so on?
Comment by Lauran — June 19, 2006 @ 1:15 pm
How does threat work with crits? I’ve heard that a crit generates threat equivalent to 150% of the actual damage. So if a Maul hit for 1000 generates 2540 threat, a maul crit for 1500 would = 1500 x 2.54 x 1.5? My head is spinning
Comment by Brian — June 19, 2006 @ 5:01 pm
What tool is used to measure threat? Is it just a matter of testing? Some numbers posted seem very specific.
Also I would be very curious to see how damage spell threat is calculated. Frost spells that slow, do they receive more threat than pure damage? How much threat does a counterspell create? Does Ice Armor generate further threat when the frost debuff occurs?
Comment by GPF — June 20, 2006 @ 5:54 am
Warlocks do not have a invulnerability spell or ability. The closest thing would be our Voidwalker’s sacrifice, which acts just like a strong shield. Our only de-aggro ability is a Tier6 5point talent called master demonology. If we have our imp out, and have that talent, we generate 20% less threat than normal.
Comment by Fireye — June 20, 2006 @ 6:45 am
Crits are nothing special in terms of threat. They do more damage, so they generate more threat, but it’s all the same formula whether you crit for 1500 or HIT for 1500.
GPF - The numbers were taken from posts on the warrior and druid forums, there were a few people who methodically went through and tested each move. They had a warrior or feral druid apply a move and then had an unarmed caster punch the mob until it aggroed onto him. they repeated each test a number of times and were able to calculate the threat value to within 1-2 points. I think they were using Recap to log the data.
Comment by Lauran — June 20, 2006 @ 6:46 am
I play(ed) a hunter, we used the kiting strategy on Razorgore. At any given run there I applied 1xDistracting Shot to a dragonkin, and I never lost aggro.
We used paladins exculsively for healing during phase 1. If that stuff there is right, they healed for less than 1200 health (or 1800, if it’s 33%). That is -not- right. They healed for at least 20 000 points of health each.
I am very much like you (I think) in the way that I like trying to figure how the game works in figures. I am a strong believer that threat decays over time, and I have yet to actually see something that contradicts that theory.
Comment by Xaddam — June 20, 2006 @ 10:43 pm
Xaddam - there have been a number of tests on if threat decays over time, and the conclusion was that it would take 24 hours for threat to decay even 10%.
Your calculations regarding the razorgore fight are a bit off. You did not take into account the 30% factor for ranged threat, and you assume a single paladin healed you throughout the entire encounter. That’s 1560 healed from a single healer with no aggro reduction skills or blessing of salvation or the horde totem version. 2340 assuming sabin is right (and I think it’s actually 25%, not 33). Add salvation or the totem on to that… and it should start to make more sense. remember that if you’re the one who initiated hate on the mob, the only heals that matter are the ones on you, and the ones on the healers who heal you (and so on up the chain of healing). If someone slept the dragon first or something, they’ll also be on its list as will anyone who heals them.
Comment by Lauran — June 21, 2006 @ 7:34 am
The only tests I have seen with decay of threat is assuming the aggroholder (tank) will loose threat - which according to what I’ve observed is not true. So 24 hours for 10% *on the tank* I can agree to, but not on any DPS/healing. (which would explain the assumption that “ranged need 30% more threat - melee needs 10%”)
I know there are a number of additional factors that would change the threat, I just skipped them - they appeared trivial to the amount of marginal that your assumptions were off. I am pretty sure - but I have done no extensive testing - that as long as your in combat you are on every mobs threat list. Ever had some one train mobs over you when fighting ‘one of their kind’? Yeah - they aggro on you after the passerby has left their aggro list. Though - might be special occasions, as I said I never did any testing on the matter. Just food for thought - don’t quote me on it.
Comment by Xaddam — June 21, 2006 @ 11:52 am
Hunters Disengage is a melee attack. Thats probably why you don’t see it used much. Since the threat reduction is low compared to the amount of damage I can do, it may take 2 or 3 Disengages (which is on a short timer) to actually disengage a mob.
So while it may work on grinding, on Core mobs I would usually be dead before Disengage got one off of me, therefore - Feign Death, which works better from a distance and - if not resisted -immediatly, also wipes all aggro so I can start damaging all over again.
Comment by Alauric — June 30, 2006 @ 12:53 pm
I was always told Sublety and Salvation do not stack, how are you sure they do?
Comment by David — July 22, 2006 @ 11:27 am
It’s been tested, David. They do stack, but as noted above, it’s multiplied, not added.
1.12 promises to make all these things much clearer… though the tooltips might be a little uglier.
Comment by Lauran — July 22, 2006 @ 12:23 pm
about taunt…
“the druid’s is a bit better because it has a shorter cooldown and costs no rage.”
warriors taunt is also on 10s cooldown (and can be reduced via talents, and cost no rage.
what taunt does - it completely overwrites threat with a value of a person on top of hate list, and makes enemy attack you for a short amount of time. having the same threat as previous person won’t make a mob stay on tank after taunt buff expires - tank needs to generate additional threat to make mob change targets.
Comment by kaukas — October 3, 2006 @ 4:20 am
I’d just like to point out, if only as an interesting fact, that warlocks also have a threat heavy spell.
Searing pain does double threat. Which means that 100 damage from searing pain = 200 threat. In PvE this spell is mostly used to save priests in trouble. (which is rare in end game)
Comment by Veon — October 4, 2006 @ 1:46 am
Thanks Kaukas. I noticed that a while back and didnt fix it til now. Stupid mistake on my part. And your description is just a shorthand version of what I explained above.
Veon, I was aware of that, but didn’t think it was particularly worth mentioning here, since this was intended to be just a basic outline of how threat works for people tanking and people trying to avoid becoming the tank. There used to be a great post on it on the R&D forums, but that’s gone now… people can read wowwiki for the in-depth details on warlock and shadow priest and paladin tanking and so on.
Comment by Lauran — October 9, 2006 @ 12:29 pm
Two quick Druid-specific comments:
“A Druid in cat form can Cower, whch reduces threat on a single target by 600, equivalent to 600 damage from the druid.”
This should actually be “…equivalent to 750 damage from the druid.”, due to the recent changes in cat-form aggro.
Regarding crits and threat, while I have not done rigorous testing, I have done some minimal ad hoc testing, and it appears (can’t swear to it, but it appears to be so) that crit Mauls do in fact generate double the expected threat. There was a comment to this effect on the old Druid forums, although I have been unable to find it since the forum reworking.
To be specific: I crit-Mauled a 7000hp mob for 600 damage, which was then melee’d down by a single rogue. 600 damage should have been 1524 threat, which would require 1676 threat to pull aggro at melee range, or 2096 damage from a rogue. However, the rogue did not pull aggro until he had done all but about 1000 of the mob’s health, or 5400 damage. He would have had to feint 3 times to accomplish that, which is highly unlikely (judging both from the speed with which he beat it down, and the fact that my aggro is normally good enough to make Feint unnecessary–it’s just that in this situation I was holding aggro on 4 mobs, so I deliberately ignored the one that I critted on the first hit). However, if crits do double threat, my actual threat on the mob would have been 3048 threat, requiring 3353 threat to pull aggro at melee range, or 4191 damage–which is just about where the rogue pulled aggro.
As I said, I haven’t done exhaustive and repeatable tests (which are, certainly, long overdue). But I watch my fights quite closely, especially with an eye to aggro generation, and it does appear to me that crit Mauls (although not regular crits, certainly, as has been well-documented on the Warrior forums) generate double the expected threat.
I’ll do the official, repeatable testing as soon as I have the time and someone to help me with it, but I’d appreciate it if you’d at least add a note that the question remains open.
*hugs*,
Qina.
P.S. Thanks for an *excellent* site!
Comment by Qina — October 13, 2006 @ 8:37 am
The cower comment is correct. The crit comment is so far as I’m aware, incorrect.. crits do double threat in a sense, only because they do double damage. The formula for crits and the formula for non-crits are identical. I’ve yet to see any substantive evidence otherwise, and the original testing which documented the druid threat formulas specifically indicated that maul crits did not have any additional threat component.
Most likely you are running into the change in mathematics that 1.12 brought about. We no longer generate 145% threat in bear with defiance equiv; it’s more like 150% now.
Comment by Lauran — October 17, 2006 @ 3:16 pm
In response to Xaddam(post
It’s not mentioned anywhere in this guide, but since heals don’t target a single mob, they don’t aggro a single mob. It wouldn’t be fair(or safe) if 1000 healing did 5000 aggro(500 x 10 mobs in range). Instead you’re looking at 1000 healing doing 50 aggro per mob across 10 mobs, for the same total of 500 aggro.
During Razorgore stage 1, when your paladins heal someone, it’s being divided evenly among the 10+ mobs currently on the stage - with that number increasing as the fight progresses. Not to mention, the majority of that threat evaporates as orcs die. In order for a healer to pull aggro over your 600 base threat, he would have to do 600×1.3 = 780 threat. Given a clean fight, and that your dragon has been out the entire time with, on average, 10 other mobs alive during a heal - a priest with no threat reduction would still have to do 15,600 points of healing to pull aggro off you.
Comment by dhugar — December 5, 2006 @ 3:34 am
Dhugar, that is not even remotely correct. Sorry, you’re dead, completely, totally wrong. Healing threat applies equally to all mobs, but it is not divided between them. 3000 points of healing is 1500 points of threat to every mob, not, say, 500 points to each of 3 mobs. Total threat is irrelavent, the only thing that matters is whether your threat is sufficiently higher than the current target that you pull aggro.
Comment by Lauran — December 11, 2006 @ 11:59 am