How Diablo hackers uncovered a speedrun scandal

For years, Maciej “Groobo” Maselewski stood as the undisputed champion of Diablo speedrunning. His 3-minute, 12-second Sorcerer run looked all but unbeatable thanks to a combination of powerful (and allowable) glitch exploits along with what seemed like some unbelievable luck in the game’s randomly generated dungeon.

But when a team of other speedrunners started trying and failing to replicate that luck using outside software and analysis tools, the story behind Groobo’s run began to fall apart. As the inconsistencies in the run started to mount, that team would conduct an automated search through billions of legitimate Diablo dungeons to prove beyond a shadow of a doubt that Groobo’s game couldn’t have taken place in any of them.

“We just had a lot of curiosity and resentment that drove us to dig even deeper,” team member Staphen told Ars Technica of their investigation. “Betrayal might be another way to describe it,” team member AJenbo added. “To find out that this had been done illegitimately… and the person had both gotten and taken a lot of praise for their achievement.”

If we have unearned luck

If you have any familiarity with Diablo or speedrunning, watching Groobo’s run feels like watching someone win the lottery. First, there’s the dungeon itself, which features a sequence of stairways that appear just steps from each other, forming a quick and enemy-free path down to the dungeon’s deeper levels. Then there’s Groobo’s lucky find of Naj’s Puzzler on level 9, a unique item that enables the teleporting necessary for many of the run’s late-game maneuvers.

Groobo’s 3:12 Diablo speedrun, as submitted to Speed Demos Archive in 2009

“It seemed very unusual that we would have so many levels with the upstairs and the downstairs right next to each other,” Allan “DwangoAC” Cecil told Ars Technica. “We wanted to find some way of replicating this.”

When Cecil and a team of tool-assisted speedrun (TAS) authors started that search process in earnest last February, they said they used Groobo’s run as a baseline to try to improve from. While Groobo ostensibly had to rely on his own human luck in prepping his run, the TAS runners could use techniques and tools from outside the game to replicate Groobo’s run (or something very similar) every time.