According to the Fiction Songfacts, this track was written by the band's drummer Jimmy "The Rev" Sullivan three days before he was found dead on December 28, 2009, making it the last song ever to be written by The Rev.
The song itself was originally going to be called 'Death', but was changed to 'Fiction', one of Sullivan's nicknames.
Now I think I understand
How this world can overcome a man
Like a friend we saw it through
In the end I gave my life for you