A Fantasy Trilogy(?) That Starts With a Seemingly Innocuous Session of a D&D-Style Tabletop Game


Possibly a Darkfriend
Years ago, when I was 11 or 12, I read a series of Fantasy novels which I remember being either a trilogy or a tetralogy/quadrilogy. Since this was almost two decades ago, I do not remember the name of either the author or any of the characters. However, I remember fairly clearly how the series starts: The story revolves around a group of three or four college-level men and women who have been involved in D&D-style roleplay gaming sessions with a Professor from their University. Unbeknownst to them, becoming familiar with the game has actually been a preparation for when the Professor (who is in fact a wizard) opens a portal into what they believed was an imaginary world. Later on in the series I remember distinctly that there was a magic sword hidden in a cave, and dragons (whom even the inhabitants of the world thought were extinct) make a reappearance. I know it's not much to go on, but the premise alone was memorable enough that I hope it rings a bell for someone. :)