Quickroot can be most easily found by entering Lornar's Pass from Beacon's Perch. He will be just to the East, on top of the hill. He shares this spawning location with Clobberhusk and Poisonbough, so it may be necessary to zone a few times in order to find him. The 6 party size and lvl 10 henchmen can prove difficult, so bring humans or heroes if possible. Because of this it may be easier to cap this skill in hard mode as opposed to normal mode, where henchmen are level 20.