Heretic
To be an atheist is, essentially, a passive action. Theists believe, but atheists do not not believe, rather, they simply persist with an absence of belief. Synonymous to how our shadows behave, it is an effortless philosophy, demanding no practice or ritualistic behavior to maintain it. Agnostic atheists are, first and foremost, skeptics, as they often prefer questions over answers, especially if proposed 'answers' cannot be proven readily. Even when it comes to more abstract, less dogmatic philosophies that do not involve deities, they find themselves pinching their chins and considering alternatives to ideas presented to them. Happily, they will consider many different ideologies. But, (and sometimes to an annoying degree), they'll play the devil's advocate as they do so, if only to illuminate multiple perspectives at once.
They resist constraints on thinking, behavior, and lifestyle choices, due to this constant desire to think for themselves. They possess a certain courage, ready to accept that death may, in fact, be simply The End, or that they truly are alone, even if believing in an alternative may make life more pleasant or bearable.
On the outside, they may seem narcissistic, or even militant against religions for not upholding any of their practices. Yet, more often than not, because of their nature as skeptics, they are the first people to say 'I don't know', preferring to leave the mysteries of the universe, of existence, of purpose, to individual consideration. This may (or may not) result in a certain humility of the heart, admitting no definitive answers to spiritual questions, and instead embracing life for its inherent value.
They are, at heart, blissfully mortal.