Dark Heart (Tales of Amaranth #1)

In Amaranth, the Wayfarers' Guild attracts all kinds of custom. When Lucan the mage walks into the stable yard with a lame horse in the rain, slave boy Tam runs to serve him -- and soon Tam wants to do nothing else. Ever.

Lucan is demanding, ruthless, devastating, in bed and out: everything Tam ever yearned for in a master. He's also master of the darkest arts, and not blind to Tam's feelings, but heedless of them. Why would a free man care how a slave feels?

When Tam's mistress asks for the mage's help because the guild is under attack, Master Lucan finds other uses for Tam: as a guide to the city, as payment to a demon in hell. But when he doesn't come back to the guildhouse one night, Tam knows the great man is in trouble - and only an insignificant slave boy can save him...