Death's Baby Sister - Bill McCurry

Fighting an insane goddess for the soul of an annoying little girl isn't how Bib the sorcerer planned to spend retirement, but someone must teach her not to turn people into sand or make it rain whales. He flees with her to find a safe place, but safety keeps getting farther away, not closer. Tragically deranged sorcerers destroy cities in their path, a crusade of murderous zealots pursues Bib, and the mad goddess makes appalling overtures to the girl. As paths of escape grow narrower, Bib must decide what he’s willing to sacrifice to succeed in saving the girl—and what he can bear to do if he fails.