Killing Hells Demon = chance to up their sickle when they die. BECAUSE they are not going to respawn (figuring there is no eye ra, bloodmage, nebula, santa, etc...), they still have however much extra damage on that death. Now if you just happened to be the unfortunate one to get last strike to proc, damage received may vary.

If they respawn however, stats for hells demon is reset. and randomized again.