Diablo Hackers Tear Through Billions of Possibilities to Debunk a 15-Year-Old Record Speedrun No-One Thought Could Be Beaten

Speedrunning has been a time-honored tradition of video game enjoyers for years, with some records being held not just for months or years, but even decades. One particular legendary Diablo run, though, has been the subject of scrutiny, an intense investigation, and now a thorough debunking.

In 2009, Maciej “Groobo” Maselewski recorded an Any% segmented run, as the Sorcerer, made up of 27 segments. The final time, at three minutes and 12 seconds, appeared on Speed Demos Archive, where no concerns were raised, and was subsequently published on February 26, 2009. It would garner two Guinness World Record entries, and Diablo speedrun attempts would proceed to decline as the run seemed nigh-impossible to challenge.

As the years went on, though, scepticism arose. In 2024, speedrunner Funkmastermp approached Allan “dwangoAC” Cecil to create a Tool-Assisted Speedrun, or TAS, of Diablo. Longtime Games Done Quick viewers will recognize dwangoAC as team leader for TASBot, the fun mascot that would appear during TAS blocks at GDQ’s charity events.

The team got to work, and as detailed in a lengthy writeup by dwangoAC and other team members, started to discover inconsistencies as they attempted to replicate Groobo’s run.

“We just had a lot of curiosity and resentment that drove us to dig even deeper,” team member Staphen told Ars Technica in a report detailing their investigation.

Because Diablo uses seeds to generate maps, it should theoretically have been possible to replicate Groobo’s run. To discover the seed Groobo used, the TAS team built a custom map tool that could reverse-engineer game seeds and determine the map, item, and quest possibilities therein. Then, a scanner tool built on top of it could sift through all the seeds and search for dungeons that might suit speedrunners.

The team searched across roughly 2.2 billion RNG seeds, attempting to recreate Groobo’s run, and couldn’t find one that imitated all the seemingly perfect generation. It seemed to indicate this wasn’t made up of segments from a single file or run, but from different runs.

The deeper they dug, the more oddities popped up; strange version markers in the main menu, inconsistent inventories, quests, and more.

In a final conclusion, the team said its discoveries demonstrate Groobo used “illegitimate means to produce the results shown in the run,” including combining gameplay from different runs, modifying memory, and using “gameplay-removing video splices.”

“Overall, the team’s analysis conclusively reveals the run was not possible as Groobo described without disqualifying modifications,” the team said. “The run should therefore be immediately retracted from all leaderboards.”

The writeup goes on to detail a response from Groobo, who told Wired: “My run is a segmented/spliced run. It always has been and it was never passed off as anything else, nor was it part of any competition or leaderboards. The speeddemosarchive page states that outright.”

The investigation team presented its analysis to Speed Demos Archive, which then discussed the findings independently with Groobo. On September 10, 2024, SDA posted an update announcing the removal of all Diablo runs by Groobo. The Diablo speedrunning community, meanwhile, kicked back into gear and started setting new records.

At a presentation, as reported by Ars Technica, dwangoAC said he pursued the investigation because “it did harm.”

“Groobo’s alleged cheating in 2009 completely stopped interest in speedrunning this category,” Cecil said. “No one tried, no one could.”

Eric is a freelance writer for IGN.