Guardians of the Flame: The Heroes (Books 4 and 5)

It had begun as an evening of fantasy gaming - college students passing the time. Then the impossible happened:

the players found themselves transported into the bodies and personae of their game characters - trapped in an alternate world where magic worked all too well, dragons were a fire-breathing menace, and only those quick enough with a sword, or their wits, survived.

The only way back to Earth was a legendary portal called the Gate Between Worlds, but there was no guarantee they'd pass through safely even if they managed to find it. And their new selves had precious little time to devote to the search; they were too busy just trying to stay alive. . .

Karl Cullinane, warrior in that fantasy game of long ago, had become a warrior in fact on This Side and won himself an empire. But the peace he'd recently established in his territories was uneasy. Certain members of the Wizards' and Slavers' Guilds would gladly destroy it, he knew - master slaver Ahrmin in particular - unless some of his own less-than-loyal subjects wrecked things first.

There had been insidious rumors that Karl meant to gain possession of a fabled wizard-killing sword - though, of course, the sword was meant for his son, Jason. The emperor understood such suspicion; it wouldn't have surprised him to hear that his old friends Walter Slovotsky and the dwarf Ahira were checking out the rumors - for their own reasons, and in their own ways. One never knew where trouble might start.

A slavers' raid on one of Karl's baronial capitals, for instance - elves, humans, and treasure taken. Was it an isolated incident or part of some larger plot?