Killing Xanathar

Not knowing what to do, you’re body seems to move on its own and unsheathes your sword and try’s to block the beam. The beam strikes the blade and the yellow energy conducts through the sword and into your arm. You feel your body become stiff as get shocked by the electricity. Then, you see one of its eye-stalks start to turn pitch black and a second beam comes out of its eye. As it hits you, you see your arm starts to turn to dust then your entire torso. You disintegrate entirely without a trace of you except there being a pile of ash where you once stood.