This mod adds Dimethylmercury to Minecraft that kills you when you touch it.
Dimethylmercury kills *Almost* anything that touches it including the Wither, that will make it easy to make Nether Star Farms, but if you touch it you will die so be careful.
The only thing Dimethylmercury can't kill (In my tests) is the Ender Dragon, so you will still need to kill the Ender Dragon yourself.
If you find any bugs please tell me.