Helms are one of the seven slots for armor. Their primary use is protecting your head and cranium, especially against mind flayers. The most popular helms to carry are helm of telepathy, helm of brilliance, and elven leather helm. Cornuthaums are occasionally used by wizards, and a helm of opposite alignment is often used on the ascension run.
The helm of telepathy grants extrinsic telepathy, similar to an amulet of ESP. HoB will increase your intelligence and wisdom by its enchantment, so +5 HoB and 18 Int and 17 Wis will produce 23 Int and 22 Wis. Elven leather helms can take a higher enchantment than other items and weigh less than most other helms: 3 wt versus 50.
List of helms
|Dunce cap||1||4||0||Cloth||Conical hat||Autocurses when worn; Int = 6, Wis = 6|
|Cornuthaum||80||4||0||Cloth||Conical hat||MC1; wizards can enchant to +7; clairvoyance and Ch+1 for wizards; blocks clairvoyance and Ch-1 for non-wizards|
|Elven leather helm||8||3||1||Leather||Leather hat||Can be enchanted to +7|
|Orcish helm||10||30||1||Iron||Iron skull cap|
|Dwarvish iron helm||20||40||2||Iron||Hard hat|
|Helm of brilliance||50||50||1||Iron||(randomized)||Int and Wis +/- enchantment amount; doesn't hinder spellcasting|
|Helm of opposite alignment||50||50||1||Iron||(randomized)||Autocurses when worn; opposite alignment|
|Helm of telepathy||50||50||1||Iron||(randomized)||Grants telepathy|
The helms marked (randomized) in the chart above have their appearances randomized from:
plumed etched crested visored
Of these, the visored helmet is always special. It protects against the blinding attack of ravens and the venom-spitting attack of cobras.
Helms made of metal provide protection against falling objects, greatly reducing the damage taken from falling rock traps, iron balls, a non blessed scroll of earth or an object you threw upwards. The helm of brilliance is the only item providing this benefit without increasing spell failure rates.
Polymorphed players or monsters with horns, such as ki-rin or unicorns, cannot equip or wear metal helmets. When you polymorph into a horned monster while wearing a soft helm you will receive the message "Your horn(s) pierce(s) through your <hat>." This does not damage or destroy your helm, though a comment in the source suggests that it someday might. There is no special message for putting on a soft helm over horns.