I'm very sorry to hear about the death, at 59 years of age, of Aaron Allston. Who was he? The designer of the best single edition of D&D ever made.
Of course, he was a better compiler and organizer than an idea man in his own right; even so, his influence on Mystara was quite enormous. He also wrote the first gazetteer (Karameikos), and contributed to the sometimes-good, sometimes-regretable "Poor Wizard's Almanac", as well as Wrath of the Immortals, which a lot of old school gamers disliked but I thought was quite good when I ran it.
Mainly, the big thing I think Allston realized was that you had to make a world where the rules of the game you've got make sense. And that's what he did with Mystara; and that's why the two are indelibly linked: Rules Cyclopedia and Mystara are literally made so that each other can make sense.
It was already a long time since he'd done any RPG work, having apparently moved on to do a series of shitty Star Wars novels. But for a while, he made my favorite edition of D&D awesome.
In any case, I'll be pouring one on the curb for Aaron Allston, and if you are a fan of old-school gaming you should be too.
Currently Smoking: Lorenzettie Quiete + Rattray's Accountant's Mixture