Thomas Moldvay (1948-2007), slayer of magical realms, helped Dungeons & Dragons grow up. His most-helpful work was as an editor for flawed product, starting with the core rules, which he midwifed into the 1981 Basic and Expert sets. Although they still needed work, mostly in scaling to higher levels; which Frank Mentzer provided a couple years later, allowing for the Companion rules to those.
For his own part Moldvay gave us X2: Castle Amber and B4: The Lost City. (He also grunted out M3: Twilight Calling, but nobody's perfect.) With Zeb Cook he is worshipped and glorified... in Mystara, as one of the two creator gods, for their summary of (then) Known World for X1: The Isle of Dread.