As mentioned in the questing soul reveal,
those who participate on the PTS for the PVP Playtest (to gather data and information on the reworked souls in 1.11 will be given the aforementioned title..)
Quoting Elrar:
Wanna kill some devs?Join us this Monday, October 15th @ 4PM Pacific (11PM GMT) and help us make the mark!
Source
EDIT: The title of the thread has the wrong date - damn typos. can a mod please amend? ty