50% increased Attack Damage while Leeching
15% increased Attack Speed while Leeching
6% reduced Damage taken while Leeching 
Brutal Fervour is a notable Ascendancy passive skill for the Slayer that grants increased damage, attack speed, and damage reduction while leeching life. It also modifies life leech effects to not get removed when the player reaches full life.
This effect does not work with Ghost Reaver, as leech effects are removed at full energy shield. In the case of instant life leech effects, such as Bloodseeker and legacy Atziri's Acuity, the leech end immediately regardless of whether you are at full life or not — Endless Hunger does not preserve or store such effects.