Seek out the mad slave to begin your test in order to unlock the real power of Death's Grip.
Find a babbling reet slave in Fens of Nathsar standing on top of a big rock about halfway between Western and Eastern Pens, ( -984, -80, 588 ) Copy/waypoint -984, -80, 588.
Hail him and listen to his cryptic babbling spoken to you in Froak.
To unlock the full potential of Death's Grip I will need to find the meaning of:
"Sennao'kees anvilteah! Sennao'kees!" -- probably anagram for "As none seek Leviathan! As none seek!"
Kill these mobs in no particular order for auto-updates. Once all 3 are dead, you will automatically receive your mythical weapon as a quest reward. The fabled warlock weapon from the previous quest will also be automatically destroyed at this point.