Rune

Using this spell, a Wizard could inscribe upon weapons mystic runes, creating various effects. Unfortunately, the process is quite unpredictable, and every item accepts runes differently. The spell is difficult to master. Those Wizards with less than 21 wisdom will be unable to cast. The delve argument can offer some insight into which runes do what on any given item, but can sometimes harm the item. Runes cannot be removed once inscribed. Valid runes for weapons are: ka, yal, vi, rin, boh, chy, era, to, nol, zor.

Prerequisite(s): none.

Syntax: cast 'rune' <object> delve.
Syntax: cast 'rune' <object> <rune>.

Rune is a spell which can only be learned by Wizards who read the Rune Spellbook.

It cannot be cast on a weapon that has been sharpened, poisoned, or has a natural ac modifier. Thrown weapons are different than weapons and cannot be runed. Once a weapon has been runed it cannot be sharpened.

Lowmort level weapons can be runed once (-10). Hero weapons can be runed twice (-15). Lord weapons can be runed 3 times (-18).

The spell Cleanse will remove runes along with other enchantments. Once cleansed of runes a weapon cannot be runed again.

When you cast rune, you can either specify a rune to imprint upon the weapon, or you can delve the weapon. Delving will give you some insight into what effect the different runes will have upon this specific weapon, but be aware that delve can return false results. Also note that delving can permanently lower the maximum hit points of a weapon, while imprinting a rune will sometimes raise the level of the weapon.

The runes you can imprint upon a weapon are: ka yal vi rin boh chy era to nol zor.

When a rune character is imprinted upon a weapon, it can become one of the following:

Rune of Battle: -3 ac, increased min & avg damage
Rune of Defense: -5 ac
Rune of Invulnerability: -10 ac
Rune of Sickliness: -2 con
Rune of Confusion: -2 wis
Rune of Weakness: -5 dr
Rune of Striking: increased min & avg damage
Rune of Vanquishing: increased min, avg, & max damage¹

Note that it's also possible for a rune to have no effect on a weapon.

If you'd like to spoil the fun of figuring out how rune works for yourself, you can check out this Rune Chart.

¹ This rune will only increase the maximum damage on weapons whose maximum damage is greater than their minimum damage.