A Lizard Walked Beside Me in the Desert

A lizard walked beside me in the desert,
demanding a loaf of bread at every step. 
And I – carrying a large sack – told him jokingly,
'My sack is bottomless – come along!'
I crossed the desert,
emptied the bread sack,
cashed in the sack of days.
And what did I beget:
a monster, slumbering on my doorstep.