Critical hit

Critical hits occur when a creature rolls a natural 20 on an attack roll. Critical hits automatically land regardless of the target's armour class, and the attacker also rolls twice the normal number of dice to determine damage dealt.
While initially a mechanic subject purely to the whims of luck, a number of features, abilities, and items allow the player to manipulate the odds of scoring a critical hit. Combined with effects that make critical hits themselves stronger, building around critical hits can be a valid strategic option.
==Mechanics==
Any ability that uses an attack roll, including spell attacks, is capable of landing critical hits. Any dice that are rolled for damage, including additional dice such as those from smites or combat manoeuvres, are rolled twice. Abilities with multiple attack rolls like or can have multiple critical hits, with each attack rolling independently of one another.
Flat modifiers and bonuses to damage – including the creature's relevant ability score modifier and proficiency bonus – are not doubled. Creatures whose attacks deal a flat amount of damage rather than a die roll, such as Familiars, can roll critical hits but do not deal extra damage on them.
==Reducing critical threshold==
Some feats, passive features, and items reduce the critical hit threshold by 1, allowing the creature to land critical hits by rolling either 19 or 20 on attack rolls. Multiple sources of this effect stack, allowing the critical hit threshold to go even lower than 19.
===Equipment===
====Weapons====
* → Improved Critical
* → Elegant Duellist (while off-hand is empty)
* → Organ Rearranger
* → Improved Critical
* (while the weapon is )
====Cloaks====
* → Stealthy Critical (while )
====Armour and headgear====
* → Covert Critical (while Obscured)
* → Covert Critical (while Obscured)
* → Deathbringer's Sight
===Conditions===
* - Critical threshold reduced by 2, available only in the The Dark Urge origin.
===Consumables===
* - Reduces the number needed to roll a Critical Hit by 1.
===Class features===
* - Level 3 passive for the Champion Fighter subclass.
===Feats===
* - Spell attacks only.
===Illithid Powers===
* - Target's critical threshold is reduced by 5, but it is also vulnerable to all damage.
==Maximising critical hit value==
===Increasing likelihood of critical hits===
Any effect that triggers a re-roll of an attack die will increase the likelihood of landing a critical hit. Attacking with Advantage almost doubles the likelihood of rolling a critical.https://statmodeling.stat.columbia.edu/2014/07/12/dnd-5e-advantage-disadvantage-probability/ Features that allow for situational rerolls, like , similarly increase the odds. Reducing the critical threshold increases chances of scoring a critical hit accordingly; taking into account advantage and multiple attacks, the odds of hitting at least one critical with a character in one round of combat are as follows:Guide:Book's Guide to Crits
Critical Hit Threshold	Chance without Advantage	Chance with Advantage	Two attacks with advantage	Three attacks
(two main+off-hand)
with advantage
20 	5% 	9.75% 	18.55% 	26.49%
19 	10% 	19% 	34.39% 	46.86%
18 	15% 	27.75% 	47.8% 	62.29%
17 	20% 	36% 	59.04% 	73.79%
16 	25% 	43.75% 	68.36% 	82.20%
15 	30% 	51% 	75.99% 	88.24%
14 	35% 	57.75% 	82.15% 	92.46%
===Additional effects on critical hit===
On the other side of things, some effects add add additional value to critical hits when they occur.
====Passives ====
* and add an extra damage die to the damage of the attack, i.e. an attack dealing will critically deal . Additional damage dice, like those from battle manoeuvres, are not subject to this additive bonus, with the exception of .
* rerolls damage die for two-handed melee weapons, when rolling a 1 or 2.
* enables an attack using a bonus action, after a critical hit.
* possibly frightens enemies on critical hit.
* rerolls all damage die twice.
====Actions and spells ====
* paralyzes a target on critical hit, once per long rest.
====Equipment====
* inflicts on critical hit.
* inflicts on both target and user on critical hit.
* adds to critical hits, itself doubled as it is adding an additional damage die.
* adds a flat damage boost of 7 to critical hits.
* knocks creatures prone in a radius on critical hit.
* restores a level 1 spell slot on critical hit.
* adds a flat damage boost to critical hits and adds temporary hit points.
* adds a flat damage boost of 7 to critical hits.
* adds a flat damage boost of 7 to critical hits.
===Guaranteed critical hits===
There are also several ways to guarantee a critical hit.
* against creatures
*, on the next attack made from within melee range
* once per Long Rest after killing a creature
* once per Long Rest
*Melee-range attacks against or targets
**
**
** 
* once per Long Rest after consuming the +3 bonus from 
*
==Negating critical hits==
Some equipment prevent attackers from landing critical hits on the wearer when worn. When a natural 20 is rolled on an attack roll against the wearer, the roll is simply treated as a 20 while still being affected by the wearer's armour class. With a high enough armour class while wearing equipment that prevents critical hits from being landed, it is possible to always be missed by attack rolls, even if a natural 20 is rolled.
===Equipment===
====Armour and headgear====
*
*
*
*
*
====Shields====
*
==Notes==
==See also==
*Advantage - For more on the calculations behind critical successes, misses, and advantage.
Category:Gameplay mechanics