Talon's abilities wound champions and epic monsters for a short duration, stacking up to three times. When Talon basic attacks a fully wounded target, they bleed for 75-245 (at levels 1-11) (+2.0 per bonus attack damage) physical damage over 2 seconds.
It should be called Mercy if the passive is something like : Talon deals 10% additional damage with his autoattacks to any target with health bellow 25%.