A tough, off-road run. 10 - 12 miles and lots of mud! As the website says:
Brooks HellRunner offers trail running at its toughest and most enjoyable. 10 -12 miles of challenging off-road running… tough, twisting trails… including the famed Hills of Hell and the Bog of Doom!
The Finish will bring redemption… but only to successful HellRunners
Hellrunner Website (opens in new window)