Amulet of harm
|This unholy amulet contains a vicious spirit that increases damage dealt to and by its wearer by one fourth. The spirit wants only to spread harm, and removing the amulet will cause the spirit to punish the wearer with draining.|
Wearing an amulet of harm makes you deal 25% more damage than normal, but also increases the damage you take by 25%. The damage is increased after AC and resistances are accounted for, but before deep dwarf damage shaving. All forms of damage, including torment, are affected. Removing the amulet has a draining effect.
Whether or not an amulet of harm is worth using greatly depends on the character. Characters with good defenses, especially AC, may appreciate the extra damage they're able to do while ignoring most of the negative effects. Characters with good ranged attacks, who deal damage at a distance more often than they receive damage, may also benefit.
The amulet of harm was added in 0.18.