The Heir Apparent: Guardians of the Flame, Book 4 (Unabridged‪)‬

Karl Cullinane and his fellow Earth-exiles Andrea, Ahira, Walter, and Lou had succeeded beyond their wildest expectations in the years since a wizard's spell had cast them into an alternate world where magic and dragons were real. Now Karl was Emperor and his son Jason was of an age to begin learning the realities if war and leadership. And with the aid of dwarves, elves, humans, and one sarcastic dragon, Karl and his friends had freed many from the evil specter of slavery and were pledged to fight till slavery was at an end.

But their actions had made them some extremely powerful enemies, chief among whom was Ahrmin of the Slaver's Guild. And for Ahrmin the time of final reckoning had at last arrived.

With or without the aid of the Guild, he would draw sword and take blood vengeance on Karl and Jason Cullinane and all they held dear....