The all-star creative team of writer Michael Fleisher and artist John Buscema continues its stellar run in ''The Chronicles of Conan Volume 20,'' with one exciting difference - John Buscema not only lends his legendary artistic touch, but also his own original story ideas and plots for several of the issues. Fleisher's polished dialogue makes these stories the ultimate marriage of concept and execution. With Gary Kwapisz lending his pencils to one issue and two stunning covers, and esteemed embellishers Ernie Chan and Steve Leialoha inking Buscema, this volume is a can't miss for Conan fans. Conan confronts some of his most difficult challenges yet when he faces down a werewolf who is being protected by the same tribe that it aims to destroy in ''Night of the Wolf,'' and he finds a hidden Cimmerian valley filled with the vestiges of an ancient war in ''Vale of Death.'' The wandering barbarian will also have to keep his wits about him if he is to keep from becoming a statue in a madwoman's collection in ''The Cauldron of Doom!''