There are two sisters, one who is dying and the other who drains other’s life forces in order to keep her sister alive. The sister who murders is known as the Pale Hand and is notorious for draining life with a single touch. Her targets are corrupt individuals, usually, priests or the Graced who abuse their wealth and power.
The Graced are people blessed with gifts that manifest by age seventeen. There is the Grace of Mind, the Grace of Heart, the Grace of Blood, and the Grace of Sight. You can heal with the Grace of Blood but most who learn it are sworn to never use their ability to kill. The Grace of Blood effects the life force, the meha, in the blood.
The Pale Hand has the Grace of Blood.