Gain Adrenaline for 20 seconds when you reach Low Life if you
do not have Adrenaline
Recover 25% of Life when you gain Adrenaline
Remove all Ailments and Burning when you gain Adrenaline 
First to Strike, Last to Fall is an Ascendancy passive skill for the Champion that causes attacks to apply Intimidate against enemies on full life, causing them to take increased attack damage. It also grants Adrenaline whenever your life is brought to low life, which grants a large bonus to damage, speed, and physical damage reduction, while also removing ailments and burning damage and recovering life.
Adrenaline is only gained when the player goes from not being on low life to going to low life. In other words, it won't activate if you are already at low life.