Picture of an one-handed flail, but instead of a spiked ball at the end of the chain, there are two hollow hemispheres made of beryllium. One of the hemispheres contains a solid ball of plutonium. They are connected in a way, so that when using the flail, they will cling together and form a complete sphere around the plutonium.
The caption reads:
The Demonstar
1d8 bludgeoning damage, plus 30d12 radiant damage to all creatures within line of sight (non-magical, and attuning to it kills you)
Ha! You may not win, but they won’t either!