A new way of showing the credits, Development Hell is a rarely spawned level that can appear on Nightmare difficulty or above, and features a group of zombies with the names of the Diablo III game developers.
"Development Hell" is a pun on Development hell, an abnormally long period of development for computer games or other various forms of electronic media.
Development Hell is found in the Cemetery of the Forsaken, as one of the defiled crypts.
This crypt features a variety of zombies - Ravenous Dead, Retching Cadavers, Hungry Corpses, and one giant Unique Unburied named Jay Wilson (former lead director of the game). All monsters have the names and jobs of the game developing group.
Killing Jay Wilson grants a hidden achievement - "Smash, Jay, Smash", placed in "Feat of Strength" group on the achievement page, plus a sigil of a horned demon.