What British games manufacturer publishes "White Dwarf," a magazine which gave Dragons of Mystery a middling review?
Dragons of Mystery: Dragons of Mystery is a "Dungeons & Dragons" sourcebook published in 1984 as part of a series of modules for the "Dragonlance" (DL) campaign setting. Dragons of Mystery:  The sourcebook received middling reviews from "White Dwarf" magazine. White Dwarf (magazine): White Dwarf is a magazine published by British games manufacturer Games Workshop, which has long served as a promotions and advertising platform for Games Workshop and Citadel Miniatures products.
Games Workshop