Each role has a specific penalty for wearing metal body armor, which is added to the difficulty level of each spell cast. Wearing a robe will reduce this penalty by half.. If you do not wear metallic body armor, the robe will instead decrease the spell difficulty by your role's penalty amount.
Aligned priests (and high priests) each have a 6/7 chance of being generated with a robe, which you can then obtain by killing the priest. If you have a sufficiently strong pet, or are willing to accept the murder penalties yourself, this can be a good way to obtain a robe without wishing or polypiling for it.
A robe can be worth keeping at your stash for any role, even if you intend to use your cloak slot for another cloak such as a cloak of magic resistance. Taking off all your metallic armor and your shield and wearing a robe (and possibly a helm of brilliance) can allow even a non-casting role restricted in their schools to cast certain useful item-management spells like identify, remove curse, and drain life.
A robe is particularly useful for wizards to offset the spellcasting penalty of wearing gauntlets of power. As wizards are often low in both strength and constitution, and tend to wield Magicbane and/or carry the Eye of the Aethiopica, they can easily choose a robe over a cloak of magic resistance and get increased carrying capacity from the gauntlets of power.
Robes in SLASH'EM
Robes in SLASH'EM are not like robes in vanilla NetHack. They are worn in the body armor slot, but do not interfere with, nor enhance (excepting the robe of power) spellcasting or a Monk's martial arts. As such, robes in SLASH'EM are no longer highly sought after in an Ascension kit (except for monks who choose not to suffer the to-hit penalty for wearing body armor).
There are several new types of robes in SLASH'EM:
- A robe of power enhances your spellcasting ability (its enchantment makes no difference).
- A robe of weakness sets your strength to 3 (plus any bonuses from rings of gain strength), except that wearing a robe of weakness and gauntlets of power simultaneously has no effect on your strength.
- A robe of protection offers 5 AC.
Robes are not randomly generated, but ordinary robes can be found on wraiths, wights, barrow wights and Nazgul, and robes of all types can be found on priests.
Robes are the only garments, apart from Shirts, ever to have
sleeves. They have three uses:
1. As the official uniform of Priests, Priestesses, Monks,
Nuns (see Nunnery), and Wizards. The OMT [ Official Management
Term ] prescribed for the Robes of Priests and Nuns is that
they _fall in severe folds_; of Priestesses that they _float_;
and of Wizards that they _swirl_. You can thus see who you
are dealing with.
2. For Kings. The OMT here is _falling in stately folds_.
3. As the garb of Desert Nomads. [...]
- makemon.c#line568 (aligned/high priest starting armor)