I have a bomb planted in my chest

Death does not scare you, you serve a purpose and you will fulfill it at the cost of your life, weather it be to cause chaos, to spread destruction or to keep secrets. you gain the following benefits

+1 constitution 

As an action, or as a reaction when you are reduced to 0 hit points you may cast fireball centered on yourself at a level equal to your proficiency without expending a spell slot or requiring any components, once you use this trait you immediately drop to 0 hit points and fail 3 death saves and cannot use this ability again until you finish a long rest