Spirit Mastery is a passive Voodoo Staff ability (not a hex) that increases the amount of damage done by any Voodoo hex attack. Unlocks at Voodoo Staff - Level 17

Increasing this ability increases the damage even more.

Rank	Damage Increase
Level 1	5%
Level 2	10%
Level 3	15%
Level 4	20%
Level 5	25%