fantasy dragon/phoniex tattoo

it's a fantasy book that involves a boy growing up in a city that reveres a fire god, there is a magician/wizard involved that gives the boy a tattoo of a phoniex or a dragon, the boy gets possessed by the fire god and starts to burn the city. he leaves the city and starts the life of being a merchant. and that pretty much all i can remember about it. oh and the magician is being chased by a water elemental because he ran away instead of trying to help save atlantis

That reminds me vaguely of Peter Dickinson's short story "Salamander Man" that appears in the anthology Fire.

This is The Burning City by Larry Niven and Jerry Pournelle. Absolutely 100 % sure.