Grasp of the Undying (Season 2016 Mastery)

Tier 6 (keystone) Resolve Mastery (1 point max)

Every 4 seconds in combat your next attack against an enemy champion steals life equal to 3% of your max health (halved for ranged champions).

(Note that this steals life, so it also deals 3% of your max health as magic damage to the attacked champion).