While you are wielding this weapon and Raging, at the beginning of your turn, roll a Storm Die (1d12) and set it aside. This Storm Die also counts as a Fury Die (but doesn't count towards your maximum number of Fury Die). If you would spend a Fury Die, you must spend your Storm Die if you still have it.

If you would roll a Storm Die and still have one set aside, instead a bolt of lightning strikes you. All creatures within Range: 3 (including yourself) must make a DC 10 STR save or take 8d8 lightning damage (save for half).