From Guild Wars Wiki
— In-game description
Vampiric strength is an unofficial term for the inherent modifier that boosts damage by 14...15% at the expense of one pip of health degeneration. It can only be found on weapons that drop in Prophecies or Factions.
- Players usually refer to weapons with this mod as +15/-1.
- The effects of this enhancement stack with the 20% damage bonus received from a customized weapon.