Skill description
When slotted on either bar, your Light and Heavy Attacks generate a stack of Grim Focus, increasing your Weapon and Spell Damage by 30, up to 10 times. Fully-charged Heavy Attacks grant two stacks.
When at 5 or more stacks, you can consume 5 stacks to fire a spectral arrow to deal 4182 Magic Damage and heal for 33% of the damage dealt, if you are in melee range.