Sigma is the alias of Siebren de Kuiper, a character who first appeared in a 2016 update for the video game Overwatch, a Blizzard Entertainment–developed first-person shooter, and the resulting franchise. Designed by artist Qiu Fang, he was introduced in a 2019 update for the title.

The skill kit for Sigma was designed to create another slow-moving anchor tank, similar to Reinhardt and Orisa, which the team would focus around; at the same time, they worked to develop this kit to avoid too much overlap with Zarya, particularly with her ultimate Graviton Surge skill.^[3] The team also knew they wanted to make this tank character related to Talon, establishing the basics of the hero concept early on.^[4] However, following the addition of Baptiste as Hero 30, Blizzard had anticipated the next hero would be Mauga, a character introduced in Baptiste's origin story, "What You Left Behind". Blizzard wanted to introduce Baptiste and Mauga back-to-back. However, as they neared release, Blizzard found that the kit did not make sense for the personality they had given Mauga. Rather than revamp the kit, they decided to develop a new character that would be better suited for the kit, holding off on Mauga's release as a hero for a later time.^[5] Blizzard quickly focused on an astrophysicist, which would readily tie into the gravity-based kit, and then adjusted the kit to incorporate additional gravitational powers that fell in line with the new character while further distinguishing his kit from Zarya's.^[4][3] They subsequently gave Sigma a tragic backstory as a villain who is unaware he was being used as a tool and as a weapon of mass destruction within Talon; whereas Baptiste had been in the same situation, Baptiste had the mental stability to walk away, while Sigma's ongoing dementia kept him working for Talon.^[5][3] On his reveal, Sigma was revealed to levitate slightly throughout the ground, and to that end, is barefoot, which drew some reaction from fans. Blizzard artist Qiu Fang explained this decision came from real-world mental health hospitals, where patients are often not given any shoes for which they potentially use to harm themselves. As such, leaving Sigma barefoot was to "sell the asylum look".^[1]

Sigma stands roughly 8 ft tall.^[6]

Like other Overwatch characters, Sigma received skins, unlockable cosmetic items to change his in-game appearance. His "Maestro" skin was designed at the time to promote an upcoming music album Blizzard was producing for the game, and felt the character would suit the event well due to his affinity for classical music. For the skin, Sigma's armor was redesigned to resemble string violins, with his hair slicked back. After the development team felt it was too sleek, they adjusted his hair to be messy, to give him an "Einstein-slash-Beethoven vibe".^[7]

Siebren de Kuiper is a Dutch astrophysicist associated with Talon. De Kuiper was a pioneering figure in his field and conducted most of his research at his laboratory in The Hague. He established a foundation for his work to where he moved onto performing further experiments aboard an international space station. However, an experiment went wrong, briefly creating a black hole that touched De Kuiper. De Kuiper sustained psychological damage from this, and strange gravitational fluctuations persisted around him. Returned to Earth, he was deemed too dangerous to release, and kept in a secret government facility for years, where he became known only as "Subject Sigma". De Kuiper retreated into his own mind, believing he would never see the outside world again. However, the Talon organization discovered his existence, and freed him from the facility, hoping to use his gravitational powers to their own end. Talon helped Sigma to regain his sanity and control of the gravitational fluctuations to use as weapons, though Sigma remained unaware that Talon was manipulating him for their own purposes.^[8]

His main weapons are Hyperspheres, gravitic projectiles that can bounce off walls and damage a small area that draw foes into the explosion, and Accretion, which gathers debris into a large projectile to kinetically throw at opponents, causing knockback. He also has two defensive abilities: Experimental Barrier, a barrier that he can deployed outward in front of him to a variable distance and then recall it, upon which it starts regenerating any damage taken; and Kinetic Grasp, which creates a field that absorbs projectiles that hit it which, upon release, coverts that into temporary health for the character. His ultimate, Gravitic Flux, allows him to fly up briefly to place a black hole on the ground. Any opponents trapped within the range of the hole are thrown up into the air for several seconds before being slammed to the ground, taking half of their maximum health on impact.^[9][10]

Following a few teasers on social media in the week prior, Sigma was formally announced as the game's 31st hero on July 22, 2019, and made available on the PTR the following day.^[10] Sigma was added across all servers on August 13, 2019.^[11]

Early reactions to Sigma as a character were positive, with fans expressing particular confusion over his bare feet, with Daily Dot writer Joseph Knoop joking the game may be catering to a particular fetish, and observing memes revolving around the confusion from the fandom.^[12] Cass Marshall in an article for Polygon meanwhile praised the character's introduction through the use of non-linear storytelling to depict his thought process. Considering it cosmic horror, Marshall described the introductory animation as verging Lovecraftian, or inspired by the Warp from Warhammer 40K's setting.^[13]

However after Qui Fang's comments came to light regarding the character's development, fans regarded the character in a more negative light, seeing him as a stereotype of people suffering from mental illness. Liana Ruppert of Prima Games stated that while the barefoot design was a solid marketing decision that brought attention to the character, she added that one could argue there were other ways to garner the same attention than to "sell" an asylum look.^[14] Meanwhile, doctors Raffael Boccamazzo and Rachel Kowert released a statement for mental health organization Take This raising issue with the stigmas that the character relied upon for his design as well as the use of outdated stereotypes regarding mental health institutions, further expressing their dismay that it was hardly an isolated incident in gaming.^[15] Gaming The Mind, a mental health organization in the United Kingdom, instead questioned Chu's statements regarding the character, stating that if mental illness was not a factor then the development team should have to answer why they relied on asylum tropes.^[16]

Psychologist Kelli Dunlap and University of York researcher Rachel Kowert discussed the character for the book Monstrosity in Games and Play. Examining how mental illness was often portrayed as villainous and monstrous, they felt Sigma's characterization fit the "Zoo Specimen" trope, an erroneous stereotype that often portrays such individuals as wildly unpredictable dangerous as well as institutions to help them as brutal and inhumane in the treatment of their patients.^[17] Dunlap and Kowert also cited Sigma as a negative portrayal of mental illness in a paper for the Canadian Game Studies Association journal Loading, suggesting that despite the developer's intentions the asylum aspect of his character and allusions too such could easily have been omitted from the character without impacting the character, narrative or game setting.^[18]

Meanwhile in their article for Polygon, Marshall described the reveal as a "gut punch" in part due to their own struggled with mental illness. While they pointed out Talon had a similar exploitive relationship with the character Widowmaker, her character was so extreme and removed from reality it was hard to see oneself in her position. By comparison, in Sigma's case much of the imagery used for his character such as the presence of restraints and confusion experienced by him were all too familiar to Marshall. While they acknowledged that it was powerful imagery, they suggested too it was some that "perhaps unintentionally trades in dangerous shorthand based on the stigma against mental illness". They added that while the presence of the character didn't ruin Overwatch for them, it served as a "an uncomfortable splinter in the premise of the game", and led them to question how the game would tackle such multifaceted characters that face problems real people experience.^[13]

Journalist Nathan Grayson in an article for Kotaku expressed dismay over the event, stating that Blizzard at the time found themselves in an awkward spot with a character he observed players were otherwise enjoying, and expressing that due to the development team's commitment to inclusivity he was hopeful they were listening to the negative response.^[16] In contrast, Bryan Lawver for Screen Rant argued that the issues with the character represented a farther reaching problem with Overwatch's development. Noting that the game early on had received significant praise for its character diversity, the portrayal of Sigma's mental issues as well as his role as yet another white character in a game illustrated a growing problem with representation in the game, particularly in light of the absence of more diverse alternatives.^[19]