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Revision as of 22:37, 9 May 2019 by Sirtheta (talk | contribs) (update for 0.23, including statistical parsing of formula (s/o to IRC for setting me straight))
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Version 0.23: This article may not be up to date for the latest stable release of Crawl.

Disruption is a special brand found only on the artefact great mace, Undeadhunter. Each time it strikes an undead target and deals damage dam, there is a 2/3 probability for the target to be blasted with disruptive energy up to an additional 3× damage (4× damage in total). On average, you deal 1.67× damage.

Damage Calculation

Additional damage is calculated according to the formula:

random2avg((1 + (dam * 3)), 3))[1]

random2avg[2] takes the average of 3 rolls, here, which means the resulting extra damage approximates a Gaussian distribution with a mean of 3/2 × dam[3] and a standard deviation of approximately 1/2 × dam[4].

Following the 68–95–99.7 rule[5], additional damage dealt is between 1× and 2× damage 68% of the time and between 0.5× and 2.5× damage 95% of the time.


Disruption was once a normal brand found on random melee weapons. In 0.4, it was removed and the holy wrath brand was enhanced instead. It was returned in 0.9 for this particular artefact.


  1. art-func.h:765 (0.23.0)
  2. random.cc:288 (0.23.0)
  3. random2avg returns an int, which shifts the mean slightly downwards from this value due to the effect of integer truncation for division in C++.
  4. More exactly: 1/2 × sqrt[(dam × dam) + (dam / 3)]. The difference between the two calculations is negligible, as the increase is between 0.08 and 0.083(3) for any dam above 1.
  5. https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule
Melee weapons AntimagicChaosDistortionDragon slayingDrainingElectrocutionFlamingFreezingHoly wrathPainProtectionReachingReapingSpeedVampiricVenomVorpal
Launchers ElectrocutionEvasionFlameFrostPenetrationSpeedVenomVorpal
Throwing weapons AtropaCurareDaturaDispersalPenetrationPoisonedReturningSilver