A quick datamining job by the folks at steamdb.info—and for the record, they've been right 100% of the time in the past—has revealed that Valve will be adding the legendary Age of Empires II: The Age of Kings to its Steam Store. But it won't be alone for the ride, as its sole expansion, Age of Empires II: The Conquerers, will be tagging along. In typical Steam fashion there will be dozens of achievements and presumably cloud save functionality to entice you to play it again and know that your progress won't be lost.
Age of Empires II made it to the number 13 spot on our Top 25 PC Games list, and with good reason. It was hailed as the best game of 1999 by several outlets and has engraved undeniable nostalgia into the minds of those who played it. If there's one thing that can be said about it that no other game in its genre can, it's that even non-RTS fans can enjoy it from the moment they're granted control of their first empire. Seeing an empire advance through the many eras of human history was a fresh take on the genre that everyone could understand, as opposed to the less tangible technology trees of other games (i.e. StarCraft).
Its developer, Ensemble Studios, closed down in 2009 after disappointing reception to both Age of Empires III and Halo Wars. It was a crying shame because the Age of Empires series, if done right, could benefit greatly from the powerful hardware of today. On the plus side, based on the image above Age of Empires II hasn't aged poorly and is a perfect candidate for your next purchase on Steam.