Hex magic
Skill-tree coverage describes Unholy Vitality as restoring Coen's health after he uses an active ability — the counterweight to a Witchcraft kit whose strongest spells are paid for in health.
The sources disagree about what kind of node this is: August 2026 coverage lists it in the tree's Abilities column while describing an effect that reads as passive. The published column is recorded, the passive reading is kept, and neither is asserted over the other until retail.