To gain this you need to play the entire game whitout using any CONSUMABLE item. That mean healing potion, healing salve and foods.
What you can use to replenish youre health are:
- The beds or any resting place
- Rings that replenish health over time
- Weapons that replenish health when you kill an enemy
- The spells Blood Toll and Blood Vortex
It may sound hard but the easy fighting system of this game and the fact that you can die as often as you want as long as you have Twiligh energy left (wich replenish by killling people with the Scythe) make this a no brainer. If you still have problem then play on easy and save often.
If you did all that it should be awarded when the credits start rolling along with any other end game achievement.