What musician performed on the album Witchkrieg and is also a member of Slayer?
Witchkrieg:  "Witchkrieg" showcases an impressive line-up of guest musicians such as Andy LaRocque from King Diamond, Kerry King from the thrash band Slayer, Hank Shermann of Mercyful Fate, Lee Altus and Gary Holt from Exodus and Jim Durkin from Dark Angel. Gary Holt (musician):  He is a guitarist and the main songwriter for the American thrash metal band Exodus and is also a guitarist for the American thrash metal band Slayer, in which he took over duties for original guitarist Jeff Hanneman, who died in 2013.
Gary Holt