It's a random spawn crypt during the quest "Shattered Crown" in Act 1. Im not sure if it spawns on Normal mode, but i have heard it only spawns randomly between Nightmare and Inferno. All the mobs inside it are named after the artists/designers/technicals.. basically all the developers of D3.
Here, have a look
As you can see in the last photo, the boss of Development Hell is Lead Designer Jay Wilson.
After killing him, you receive an achievement called "Smash, Jay Smash!"
Direct links for bigger photos:
https://i.imgur.com/LFb8S.jpg
https://i.imgur.com/N0CoD.jpg
https://i.imgur.com/NezIF.jpg
https://i.imgur.com/YSTIO.jpg