With the burst fusion, a weapon’s energy damage can form a small explosion that spills onto a second target. The weapon gains the arc critical hit effect (see page 182). If the weapon already has a critical hit effect, when you score a critical hit, you can apply either the weapon’s normal critical hit effect or the arc effect. The amount of damage dealt to the secondary target is equal to one-third the level of the weapon with the burst fusion (minimum 1). Only weapons that deal acid, cold, electricity, fire, or sonic damage can benefit from a burst fusion. If your weapon deals more than one type of energy damage, you select one of those types for the arc critical hit effect to apply to secondary targets when the fusion is added.

A weapon with the entangling fusion gains the entangle weapon special property (see page 181). Only a single attack each day may benefit from this property, and you must announce before making an attack that it is an entangle attack. Regardless of how many targets you can hit with a single attack from your weapon, only a single target of your choice is affected by the entangle condition. The entangle effect ends after 1d4 rounds if the target has not already escaped it. Only weapons that do bludgeoning, piercing, slashing, or cold damage can benefit from this fusion.

A weapon with the holy fusion becomes blessed with divine energy from a good deity. Any attacks with the fused weapon are good-aligned. Damage from the weapon bypasses DR/good and ignores the energy resistance of evil dragons, evil outsiders, and evil undead. The holy fusion cannot be added to weapons that have the unholy fusion.

The unholy fusion imbues a weapon with divine energy from an evil deity. Any attacks with the fused weapon are evil-aligned. Damage from the weapon overcomes DR/evil and ignores the energy resistance of good dragons and good outsiders. The unholy fusion can’t be added to weapons that have the holy fusion.

The axiomatic fusion imbues a weapon with divine energy from a lawful deity. Any attacks with the weapon are lawful-aligned. Damage from the weapon bypasses DR/lawful and ignores the energy resistance of chaotic dragons and chaotic outsiders. The axiomatic fusion can’t be added to weapons that have the anarchic fusion.

The anarchic fusion imbues a weapon with divine energy from a chaotic deity. Any attacks with the weapon are chaotic-aligned. Damage from the weapon bypasses DR/chaotic and ignores the energy resistance of lawful dragons and lawful outsiders. The anarchic fusion can’t be added to weapons that have the axiomatic fusion.

A weapon with the venomous fusion gains the injection weapon special property (see page 181). Only a single attack each day may benefit from this property, and you must announce before making an attack that it is an injection attack. Regardless of how many targets you can hit with a single attack from your weapon, only a single target of your choice is exposed to the drug, medicinal, or poison when you use the injection property in an attack. Only weapons that deal piercing or slashing damage can benefit from this fusion.

A weapon with the merciful fusion often hums pleasantly when at rest and makes soft, airy musical noises when it is used to make an attack. The magic of this fusion subdues the damaging effect of the weapon it is added to. While this fusion is active, the weapon’s regular damage becomes nonlethal damage. If the weapon deals two types of damage, both of the damage types become nonlethal. You can activate or deactivate the merciful fusion as a swift action.

A weapon with the spellthrower fusion is able to have a single spell gem loaded into it at a time. It takes 1 minute to load a spell gem, and only gems containing a spell with a casting time of one standard action or less and a spell level no greater than one-quarter the weapon’s item level can be loaded into the weapon.

If you are proficient with and wielding the weapon, as a full action you can cast the spell contained within the spell gem rather than make a normal attack. This allows you to use the spell gem as if you were a spellcaster with the spell on your class’s spell list.

Unlike the normal rules for using a spell gem, it does not matter if the gem’s item level is higher than your caster level (even if your caster level is 0). However, if the spell gem’s item level is higher than your base attack bonus, once you’ve spent the full action to cast the spell, you must succeed at an attack roll with the weapon against an AC equal to the spell gem’s level + 1 or you fail to cast the spell. This roll represents your expertise with the weapon, and no actual attack or ammunition is used. If you fail to cast a spell from a spell gem, the spell is expended harmlessly and the spell gem is destroyed.