Critical hit

Critical hits are special types of hits dealt to monsters (and other players in PVP). Critical hits can happen from any type of damage (weapon or spell), they deal bonus damage, and may trigger other special effects as well. Monsters that die from critical hits usually explode in an especially gruesome death animation, adding visual fun to the killing bonuses.

Critical Hits in Diablo III

Exactly how critical hits work and how much damage they deal isn't yet entirely understood. This is partially due to the fact that the game remains under development and that the features are in flux, but it's also due to critical hits doing a lot of different things in D3. In previous games in the series critical hits were simple; they doubled physical damage. In D3, the biggest change is that critical hits work on all types of damage. Not just physical, or melee, but various types of spell damage as well, and apparently they can trigger from elemental damage on weapons as well.

The basic critical hit bonus is still +100% damage, but various skills increase the damage of critical hits, while others increase the odds of critical hits scoring, or cause other effects to trigger when a critical hit is scored. How these will all interact remains to be seen.

The calculation of the bonuses is going to be interesting as well. In D1 and D2, critical hits were a huge bonus, since doubled the total physical damage dealt; a value that was often in the 1000s for a powerful combat character. In D3 critical hits will still (apparently) be that powerful for the Barbarian, but critical hits on spell damage would seem to be far less potent, since spells generally deal their damage over time, rather than in huge chunks per hit. Occasionally adding 10% to the critical hit damage of a 1-6 damage spell isn't very impressive, even if the spell is hitting 20x a second. A wizard would seem better off boosting the % chance of scoring a critical hit.

Types of damage and effects

Critical hits are a major part of the game in Diablo III, dealing double damage with every type of damage, inflicting bonus effects, boosting and being boosted by a wide variety of skills, and triggering special (extra gruesome) death animations.

• Physical Damage: Deals double damage. Might also knockback, but not confirmed.
• Arcane Damage: Critical hits from arcane damage silence targets for 4 secs. (Silenced targets can not cast some spells, such as a Skeletal Summoner or Goatman Shaman resurrecting fallen minions.)
• Cold Damage: Critical hits from cold damage stun targets for 2 seconds.
• Fire Damage: Critical hits from fire damage set targets ablaze, dealing additional damage per second.
• Lightning Damage: Critical hits from lightning damage stun targets for 2 seconds.
• Toxic Damage: Critical hits from toxic (poison) damage have an unknown bonus. Extra damage over time?

Critical Hit Skills

This is a partial list, since the game is still under development and skill descriptions and functions are bound to evolve over time. Looking at what sorts of skills add or otherwise interact with critical hits can be illustrative, though.

Barbarian

The Barbarian has a number of skills that increase the % damage of his critical hit, and a few interesting skills that boost other properties (such as fury generation rate and defense) when he scores critical hits. There aren't any known skills (yet) that increase his chances to score critical hits, though.

Juggernaut Skills

• Inspiration "increases critical hit damage by 3% and increases the damage of added hits by 5% for 15 seconds." It's not known what this description means by "added hits." The bonus to critical hit damage seems very small too. Just 3%? Would that make the total bonus +103% damage? Or do Barbarians have some value other than +100% for critical hit?

Battlemaster Skills

• Battle Rage is a buff that temporarily (15 seconds) increases damage by 100% and critical hit damage by 30%.

• Hammer of the Ancients boosts critical hit damage when using this active skill.

• Critical Attacks this passive skill boosts critical hit damage by 20%. This skill apparently boosts all critical hit damage for the Barbarian, even that inflicted by non-special attacks, and skills from other skill trees.

• Deliberate Defense. "On a critical hit, +10% armor for 15 seconds." This skill is a sign of how integral Blizzard wants to make critical hits to the game. This one boosts the defense when a critical hit is scored. It would seem to directly incentivize standing toe to toe with enemies and smacking them in the face; the more critical hits you score, the less likely they are to hit you back.

Berserker Skills

• Savage: This passive skill "Increases Fury generation 30% for 8 seconds after scoring a critical hit."

Witch Doctor

No critical hit bonuses from Witch Doctor skills are yet known. This isn't a sign that there aren't any, though. It's just due to the WD only having 11 skills on display at Blizzcon, while the Wizard and Barbarian had more than 50 each.

Wizard

Most wizard skills seen at Blizzcon (October 2008) displayed the bonus provided by a critical hit of that type of damage (cold, lightning, etc), but there were fewer skills that actually boosted or affected the frequency of his critical hits.

Arcane Skill

No skills in this tree listed bonuses related to critical hits as of October 2008.

Conjuring Skill

No skills in this tree listed bonuses related to critical hits as of October 2008.

Storm Skills

• Thunderstruck: Increases the critical hit chance of all lightning spells by X%. The bonuses listed on this passive skill as of Blizzcon (October 2008) started at 5% and increased 5% per skill rank. It's not known what the base bonus to critical hit is, for the Wizard. This skill might increase it from 0%, or Wizards might have an inherent bonus based on their Clvl, or attributes, or there might be bonuses to be had from equipment.

• Frost Nova. Projectiles have an additional 25% chance of a critical hit. Frost Nova doesn't deal very high damage, and it has a very long 12 second cool down time, so the attraction of critical hits here is clearly from the cold. (Critical hits from cold damage freeze targets.)

• Deep Freeze: Increases the critical hit chance of all cold spells. This passive spell adds 5% chance at Rank 1, and more at higher ranks.

• Lethal Energy: Increases the chance to score critical hits with melee and spell attacks. Grants a 5% bonus at rank 1. This seems like a very powerful skill, if it indeed works for all spells, including those in other trees. It's a fairly high level skill though, and would require a substantial investment into the Storm skill tree to enable it, but it might still be worth it.

Diablo III Critical Hit Items

Nothing is yet known about this. It seems likely that bonuses to the damage and/or likelihood of critical hits will be found on equipment, but how common or rare such bonuses will be remains totally unknown. It's certainly something the D3 Team will work on during development and balancing.

Diablo I and II Critical Hits

Critical hits in Diablo II were a major factor in the game, but only worked with physical damage. Critical strike was called "Deadly Strike" on weapons, where it occurred on quite a few unique items, set items, and runewords. (But not magical or rare.) A number of character skills boosted critical strike as well. All of the Barbarian's weapon masteries conveyed critical strike bonuses, as did the Amazon's Critical Strike, and the Assassin's Claw Mastery.

In Diablo I critical hits are a hidden bonus for the Warrior and Barbarian characters. They gain a 1% chance to deal double damage with each Clvl they gain. At level 20 they deal double damage 20% of the time, at level 30 they do it 30% of the time, etc.