Slaying is a term used to describe a property that increases a character's accuracy and/or damage in melee and ranged combat. It is often given in the form of a +x, +y slaying bonus, where x will be the accuracy bonus, and y will be the damage bonus. Slaying does not affect spellcasting, wand use, or anything else that isn't melee or ranged combat.
Players may sometimes refer to a character or an item as having x slaying: in that case, they mean the damage bonus, which is virtually always the more important of the two.
The total of all of a character's accuracy bonuses are added to the player's to-hit number. A random number from 1 to the player's total to-hit is checked against a monster's EV to determine if the player lands a blow; thus, it is not a flat accuracy increase that is provided, but an increase in accuracy on average.
The character's total slaying bonus is added to the "effective enchantment" of the player's weapon (and applies to unarmed combat as well). In combat, the player gets a damage bonus of 1d(effective enchantment). Unlike base damage, this bonus is not affected by the player's skill. The total damage done is then adjusted appropriately by the monster's AC, meaning that slaying can be very useful in helping to get past a monster's armour.
There are a number of sources of slaying bonuses:
- A +x, +y ring of slaying provides a bonus of x to accuracy and y to damage.
- Artefacts with the "It increases your accuracy" or "It increases your damage-dealing abilities" give slaying bonuses.
- The spell Song of Slaying provides a variable amount of slaying, depending on the toughest monster you've killed while the spell is active.
- Bracers of archery are a special case, in that they provide different slaying bonuses to melee and ranged combat: they give +5, +3 to ranged, but -1, -1 to melee.
There are also a number of slaying-like effects:
- The effect Might (which is also a part of Berserk) gives a flat +1d10 bonus to melee damage. This is somewhat different from normal slaying in that it is not added to the character's effective enchantment, but just added straight on to his or her total damage. Effectively, this means that Might gives a more consistent damage bonus than 10 slaying would, even if the average increase in damage is roughly the same.
- The spell Infusion gives a damage bonus of 2-4. However, monster AC applies to this damage bonus separately from the character's main attack, making it more akin to an extra attack with an unenchanted dagger than a slaying bonus.
- The spell Corona gives an increase in accuracy, but only against one monster. Also, the bonus (+2 to +9) is applied after the to-hit number is rolled.
- The Shining One's halo gives an accuracy bonus against creatures inside the halo.
- An amulet of inaccuracy functions somewhat like a -5 accuracy bonus, except that it affects magic as well as melee and ranged combat.
Most characters will want as much to-damage slaying as they can get. To-hit slaying is considerably less valuable - it is rarely worth using a piece of equipment solely for such a bonus.
Melee characters should highly prioritize slaying, but be rational about it: a +2 damage bonus does not make a -1 randart scale mail a worthwhile proposition on your MiBe.
Prior to 0.10, slaying bonuses for damage were added to the weapon's base damage, meaning that they would be increased by having high weapon/Fighting skill. When this was changed, slaying bonuses were generally increased to compensate.