Simply exit from Champion's Dawn into the Cliffs of Dohjok and follow the quest marker to the quarry area and kill the group of mandragors there. The group consists of four level 7-8 Mandragor and a level 12 Mandragor Boss called 'Mandragor Queen'. Once that group is dead, return the Quarrymaster Bohanna to claim your reward. Alternative: Start from Jokanur Diggings and just go straight to the queen and kill it. You will still complete the quest without having to talk to anyone.