# Disruption

**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 to undead targets.

## 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.

## History

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.

## References

- ↑ art-func.h:765 (0.23.0)
- ↑ random.cc:288 (0.23.0)
- ↑
`random2avg`

returns an int, which shifts the mean slightly downwards from this value due to the effect of integer truncation for division in C++. - ↑ 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. - ↑ https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule

Brands | |
---|---|

Melee weapons | Antimagic • Chaos • Distortion • Dragon slaying • Draining • Electrocution • Flaming • Freezing • Holy wrath • Pain • Protection • Reaching • Reaping • Speed • Vampiric • Venom • Vorpal |

Launchers | Electrocution • Evasion • Flame • Frost • Penetration • Speed • Venom • Vorpal |

Throwing weapons | Atropa • Curare • Datura • Dispersal • Penetration • Poisoned • Returning • Silver |