Frank Mentzer

Frank Mentzer brought the Epic into Dungeons & Dragons, revising Tom Moldvay's Basic/Expert Set into its full glory under the Companion (especially), Master, and Immortal rules. The AD&D crew was attempting high level play but, really, nothing compared to BXCMI until late 3e.

Mentzer also (somehow) made a coherent and mostly-playable module out of Gary Gygax's Temple of Elemental Evil.

Writing as "ExTSR", Frankie stayed in contact with the fandom at (for instance) rec.games.frp.dnd; where (for instance) he defended Moldvay's decision to include the Wight and its permadrain in Basic play.

Sadly, proving the adage that you either die a Moldvay or live to see yourself become Ed Greenwood, Mentzer got into trouble in the late 2010s for some #metoo bullshit. Skub-a-dub-dub, and all that.