TomeNET

(5.4) Application of attack-affecting item mods                                 
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While item abilities such as resistances or stat boosts are always applied,
magical mods that affect attacks might not be.
Such mods are:

+to-hit, +to-dam, extra attacks, critical hits, vampiric, slays and brands.

These mods on weapons are only applied to attacks done with that particular
weapon.
Except for 'extra attacks', which generally increases your number of attacks
and will not discriminate which weapon will be used for attacking if you are
dual-wielding - both weapons always have a 50% chance each blow.

These mods on other items, like gloves or rings, will affect all weapons,
even ranged ones, and also martial arts!
Exceptions:
 - +to-dam boni will not be applied to ranged weapons, only to melee attacks.
 - Extra attacks are not applied to ranged weapons, only to melee attacks.
 - Vampirism effect will be weaker (compare table at the end of (5.13)).