He's one and the same, and
Mordant's Need/
A Man Rides Through (not sure which you're referring to...they're the two books in the series I think you're describing) were among his "lighter" efforts!
I liked them myself, but feel compelled to clarify here that his style seems very different from Tad Williams' to me. Have you read any of Williams' work and, if so, what did you think of it?
Great avatar, by the way....