Silent protector of the castle, around long after all others have left. Wielding either water or fire, nothing shall cross this defender.

I am an entire era of humanity. Two is my formula. When I am created, it is done with labour and likely followed by ancient calamity.

I have two eyes and yet I can't see, I have no lungs and yet I can breathe, Through me you feel one of the five, Through me your memories thrive, You feel me right now as you sigh, Kindly do tell, who am I?

What can go up a chimney down, but can't go down a chimney up?

I come at the end, small but discrete, In books or your belly, I’m a supplemental treat. A vestige of old, once thought obsolete, or extra material that makes texts complete.