Cruel Weapon Fusion
(from Starfinder Armory)
The cruel fusion feeds on fear and despair. When you strike a target that is frightened, panicked, or shaken with a weapon with this fusion, the target is sickened for 1 round. When you make a successful attack that drops a foe (either by killing it or knocking it unconscious), you gain 5 temporary Hit Points that last for 10 minutes. Weapons with the nonlethal special property cannot benefit from the cruel fusion.