On-hit

From NWNWiki

An on-hit item property activates when an item makes contact with an enemy. For weapons, this means a successful attack by the wielder, with the property affecting the opponent struck. For armor, this means a successful attack on the wearer, with the property affecting the the attacker. Each contact will trigger only one on-hit property for a given item, regardless of how many such properties are on the item.

Many on-hit properties are described in terms of the effect the property causes, the DC of resisting the effect, the percent chance of the property triggering, and the duration of the effect. For example, the property called "On Hit: Confusion DC-22 50% / 2 Rounds" will trigger for 50% of the successful attacks, and if it triggers, the target must make a DC 22 saving throw or be confused for 2 rounds. (The type of saving throw is not mentioned in this sort of description.)

The darkfire, deafening clang, and flame weapon spells add on-hit properties to melee weapons. The bless and bless weapon spells add an on-hit property to bolts.