Kill or Be Killed

When you would sustain fatal damage, you instead fly into an unstoppable rage, becoming unkillable and immune to movement-impairing effects for 8 sec as you seek revenge on your would-be killer. If you kill your killer in that time, you emerge from your blind rage triumphant, with at least 20% of your max health intact. If you are not victorious, you die. This effect can only occur once every 5 min and if your killer is alive when you sustain fatal damage.