You can complete this one easily by losing a duel with a friend and insta potting back up (silver pots, the ones you buy from NPCs).

Alternatively, you can drop down to this spot in Seuth Valley (North Kurzan). The lava there drops you down to 1HP but doesn't kill you. Timing the pot can be a bit tricky as it's not instant. Take off all your gear/stone/etc to make it easier.