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Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →A celebrated 3:12 Diablo Sorcerer speedrun looked almost impossible to reproduce. Investigators eventually made a detailed technical case that its 16-level video combined gameplay from incompatible runs and seeds. The case turned on more than improbably good luck: they reverse-engineered Diablo’s map generation, searched the game’s valid random seeds, and found discontinuities that the run’s segmented format did not explain. Speed Demos Archive later banished the submission, barring new developments.
The record that resisted replication
Maciej “Groobo” Maselewski submitted a 3-minute-12-second Sorcerer run to Speed Demos Archive (SDA) in 2009. The video covered 16 dungeon levels and, according to the investigation report, was assembled from 27 segments. Diablo had been released in January 1997.
The run’s apparent speed depended on unusually favorable circumstances, including a Naj’s Puzzler unique staff found on level 9. The staff enabled the teleporting used in the run. When TAS authors working on a Diablo tool-assisted speedrun tried to reproduce the map and item luck, they began investigating how the game generated levels and placed items. That effort developed into a technical examination of the submitted video.
Investigator Stephen Wills, known as staphen, described the motivation to Ars Technica as: “We just had a lot of curiosity and resentment that drove us to dig even deeper.” The team consulted the DevilutionX community and built a tool that analyzed a disassembled Diablo executable. It could inspect generated maps, item distributions, and quest placement for different seeds.
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What the seed search showed
In the investigators’ account, a seed corresponds to the second when a save was created. Since a game’s seed determines its generated content, comparing a video’s maps and drops against valid seeds offered a way to test whether the apparent luck could have come from one continuous game.
The team searched roughly 2.2 billion valid seeds, a search space reported by Ars Technica from the investigators’ work. It found no valid seed that produced the reported Naj’s Puzzler drop on level 9. The investigators said matching drops appeared with seeds associated with 2056 and 2074—dates beyond the game’s valid date range. This was evidence about the investigated run, not an independently verified probability that any Diablo run could produce such an item.
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The seed result was only one strand of the case. Investigator Anders Jenbo, known as AJenbo, told Ars: “Normally you would only need to identify a single level to replicate a run since all the other levels are generated from the same seed.” Instead, the team reported that levels in the video came from different seeds. Ars summarized the analysis by saying only two levels had been identified as coming from the same run.
The other discontinuities investigators reported
The report examined more than maps and item drops. It described inconsistencies across the video that, in the investigators’ view, could not be reconciled as one continuous game state.
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- Version indicators: Title screens and menus showed incompatible game-version clues.
- Dungeon sequence: The levels appeared in an invalid sequence.
- Inventory and quests: Items disappeared or failed to match between sections, and the video showed impossible quest combinations.
- Missing or conflicting gameplay: The report identified missing gameplay, inconsistent item drops and music, and shop reroll anomalies.
- Different character and technique evidence: The investigators noted inconsistent glitch use and fireball damage that did not match the shown level-12 character.
Taking these issues together, the team estimated that at least 13—and probably 15—separate runs had been spliced into the 16-level video. That number is the investigators’ estimate, not a finding by a court or an independent adjudicator.
Why “segmented” did not resolve the case
Groobo’s response, as reported by Ars, was that the video was “segmented/spliced” and had never been represented otherwise. An archived SDA submission described 27 segments appended into one file. He also argued that the run was not part of a competition or leaderboard. WIRED had reported in August 2024 that Groobo denied wrongdoing and called the scrutiny a witch hunt, maintaining that the run was understood to be segmented.
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Segmentation means a run can be recorded in separate attempts rather than one uninterrupted take; it does not automatically make any edit acceptable under a particular leaderboard’s rules. The investigators’ answer was that SDA allowed segments but required continuity between them and generally prohibited manually editing game files. On that basis, calling the video segmented did not account for the incompatible seeds, changing state, or other anomalies they documented.
The investigation report says its authors tried to contact Groobo through multiple channels while preparing their analysis and received no reply. That account describes the team’s outreach at the time of its report; it does not resolve the dispute beyond the evidence and responses reported by the sources.
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What SDA did—and what was known about Guinness
In February 2025, Ars reported SDA’s position: “it has been determined that Groobo’s run very likely does not stem from only legitimate techniques, and as such, has itself been banished barring new developments.” That was the archive’s ruling on the submission, not a criminal finding.
At the time Ars published its report, Guinness World Records still listed the record. Ars later added that Guinness was aware of the findings and looking into them. Those statements establish the status reported in February 2025; they do not establish a later Guinness decision.
Why the investigation mattered to Diablo speedrunning
Ars quoted investigator Allan Cecil, known as dwangoAC, saying: “Groobo’s alleged cheating in 2009 completely stopped interest in speedrunning this category [of Diablo].” Ars also reported that new runners were setting records on confirmed legitimate seeds after SDA’s action. That describes Cecil’s account and the contemporary report, not a quantified measurement of participation or a proven causal estimate.
The investigation’s strength came from making its claims testable: it explained the game mechanics, laid out how the seed search worked, and connected that result to separate inconsistencies in the video. A famous time and an established reputation could not substitute for a reproducible explanation of how the run was made. The result was a detailed community evidence case and an archive decision—not a criminal judgment.
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Sources: Kyle Orland, Ars Technica, February 15, 2025; Diablo TAS investigation team, “Analysis of Groobo’s Diablo WR Speedrun”; WIRED, August 2024.
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