Diablo II
Diablo II launched in 2000, with vastly larger scope than the original. Four acts span environments from Middle Eastern deserts to Amazonian jungles, following a wandering hero chasing the corrupted Dark Wanderer toward a confrontation with Diablo's brothers, Mephisto and Baal.
The folks at Blizzard North were chagrined by how much help (art, programming, design, etc.) was required from Blizzard "South" (AKA "original Blizzard") to finish Diablo I, so they did all the development work themselves for Diablo II, though we did have a lot of input on the design.
I was leading battle.net. Strike that, I was the only person on battle.net. And so my role for Diablo II was to write the battle.net components required for their game to handle matchmaking and support client-hosted servers, and later battle.net hosted servers.