Doc Scratch

 is an officer of and the first guardian of Alternia, meant to protect the planet, as well as facilitate the planet's "ultimate purpose". He HS 4102 (communicates) primarily with Vriska Serket via Trollian. He also communicates frequently with Rose Lalonde in her session, and has made visits to Kanaya Maryam in person. He uses pure white text and no chumhandle or trolltag, making conversations difficult to read without highlighting.

Being [] omniscient, he is an extremely skilled manipulator. He fits into the billiards concept introduced by as the cue ball, and his name is an obvious reference to the pool term for pocketing it. This relates to how would die in order to bring forth. It may also play on "Old Scratch," a traditional name for Satan, which relates to his role as "The Devil" in the story of the Ancestors. "Scratch" also means "to erase or eliminate", which reflects 's role as the demon that will destroy the universe. Like his master, HS 5520 (is not his true name), rather, it is merely a pseudonym.

appears as a humanoid figure in a white and green suit with a white handgun. His head is shaped like a cue ball, though the lack of an outline makes it look less like a ball and more like a hole in space.

Creation
Most of his genetic code came from a ~ATH book that a doomed timeline's Gamzee Makara had written in with the blood of his co-players. The book was retrieved from the alternate timeline by an Aradiabot, but was taken by the Black Queen's agents, along with the Flarp books that other, smaller pieces of his code were stored in. Similar to how Becquerel had been created by Rose's code and a dog's paradox slime, Scratch was brought to life in the later stages of the session by Team Charge's   codeHS 5500, Team Scourge's   codeHS 5503, and the ~ATH book's  codeHS 5507, along with the paradox slime of an all-knowing cue ball and Lil Cal by the Black Queen. He was HS 5513 (later brought to Alternia) by the first meteor to travel there in its planetary timeline, and the last in the trolls' Reckoning.

Pre-Hivebent
He lives in a fancy apartment composed entirely of shades of green on the green moon of Alternia. His "computer" is a typewriter that inexplicably communicates with actual computers. The messages he types and receives are printed on a sheet of paperHS 4156. Also in his apartment are a pistol and holster, several complicated chessboards all resembling different forms of the Battlefield, the ~ATH manual (which is being used as a scrapbook containing images from various timelines), and no doorbell. After all, why would an omniscient fellow need to be alerted to the presence of a visitor?

During the events of Hiveswap, it is most likely he was the one who sent Xefros Tritoh an encryption software called Scratchware so that he and Joey Claire could communicate over chatroom with total privacy from third-party surveillance. He is also implied to be the character behind the Hint system when it quips on Joey being in its "neighborhood".

is responsible for visiting young Kanaya and facilitating her awakening on Prospit. Later, he manipulates Vriska into attacking her friends Tavros and Aradia. He personally distracts Aradia and Terezi from helping Tavros simply by standing near them during their Flarp session. He did this in order to facilitate the cycle of revenge that would eventually lead to his own creation, thus ensuring the path of history.

After the Black Queen is exiled to the Alternian wastelands during the trolls' Sgrub session, she is "given a new purpose" by, who teleports to the wastelands where she roams. He makes a deal with her that ties her life to the life of the trolls' universe, causing it to end when she dies, and she becomes.

Post-Hivebent
After arranging the events of Hivebent, he works out a plan with Rose, guiding her along a path she is led to believe would destroy the Green Sun, killing Bec Noir and himself. suggests that the reason for Rose being sidetracked from paying attention to her friends, harsh methods of learning about the game, and the origin of her black magic powers were caused by unconscious manipulation by the Horrorterrors, so he advises her to ask the Cue Ball for information rather than them or the trolls. He specifically encourages her to ask it if the Outer Gods were evil; whether the answer to that question is inscrutable or not, Rose viewing the Cue Ball's answer to that question causes her to "go Grimdark", the most notable effect of which is to seek revenge on Jack.

At around the same "time," the trolls' version of Jack, Spades Slick, has finally tracked down, continuing his mission from the Midnight Crew Intermission to destroy. eventually loses omnipatience with Slick trying to bludgeon him over his dome curls the metal weapon into unusability and offers Slick to partake of a bottomless supply of licorice scotty dogs before asking him something.

When Terezi scratches Homestuck's second disc the comic gradually becomes more glitchy to the point of "unplayability" and the reader is forced to consult, offering to repair the damage before the Scratch happens and telling the story while the disc is repaired.

shows what would occur if Vriska wins the flip and Terezi lets her go, where she is stabbed by Terezi instead. After Slick breaks the grandfather clock and Vriska dies, proceeds to grab his book and hit Slick with it so hard that it breaks in half, uppercutting him out of a window.

After Slick lands on a nearby building, lands next to the wounded Slick, pulls out his revolver and aims at him, but instead turns the gun and points the handle at Slick, requesting that he kill. He then teleports Slick to a currently unknown location, as well as himself back to his home where he decides to clean up the mess he made, fixing his scrapbook that he broke as well.

is interrupted during the middle of cleaning by a banging noise, and he leaves to investigate it, permitting the reader to look through the clippings left from his scrapbook that remain on the floor. The source of the noise turns out to be a young Handmaid, Aradia's ancestor, dressed in a Felt outfit and attempting to break the fifth wall with a chair. She attempts to assault him, to no avail, and he bludgeons her with a broom, turning off the wall. He then tells the story of the Sufferer, Karkat's ancestor, as well as the stories of the ancestors related to him. During his story, Aradia's Ancestor turns on the fifth wall remotely, and Andrew Hussie breaks into 's manor. The rest of the story up until the end of the next paragraph has.

While continues his story, our author makes his way through his mansion, encountering the Wolf Head in addition to the scrapbook pages and the bowl of  command candies. After eating several of the candies and taking the rest, HS 5973 (Hussie assaults) with his own broom while the Handmaid flees. , while Hussie is assaulting him, becomes inanimate and resembles a lifeless puppet, and has his right leg ripped off by Hussie as a result. This references the Lil Cal Puppet part of his ectobiology.

After being rendered unconscious at the hands of Hussie, and after the destruction of the Alternian Universe, he dies as emerges from within him, with  having used  as a vessel the whole time. At this time, continues to be an "excellent host".

When Rose succeeded her plan, it is revealed that tricked Rose to create the Green Sun instead of eliminating it. She should've asked better questions. Suckers.

Personality
was developed by Hussie with a in mind. It is no surprise, then, that he is a master at manipulating people and events to his own ends, leading Alternia to live a radically different life than its pre-Scratch counterpart did. From extremely radical changes like introducing a Horrorterror onto the trolls' home planet to more cosmetic changes such as the addition of his own green moon, seems determined to leave his mark. Hussie aptly describes the planet as 's HS 5963 (troll fanfiction), with changing details of the original planet but keeping the same people.

is self-assured and believes himself better than amateur manipulators like Vriska and Equius, as unlike them, HS 4144 ("He never lies"), and he always plays with his cards face up. He also seems to be extremely intelligent and composed, as during the very same conversation with Vriska, he states that even though he tells Vriska what his next moves will be during their matches, she still can't beat him. This is because he is an expert manipulator of people but does not rely on deception to accomplish it—a skill that Vriska envies in both and Terezi.

The fact that he writes in the color white and that he has no Pesterchum handle (due to typing on a typewriter) indicates that he prefers to remain an anonymous party and work behind the scenes, carrying out his schemes with the least amount of influence possible. He doesn't want to be directly involved in the happenings that lead to fulfilling the planet's ultimate purpose, nor to his employer's entry to the universe, and therefore prefers to coerce others to do it. Figuratively speaking, he seems to consider others to be less than players, mere pieces to be moved into place—or perhaps billiard balls which, when struck by the cue ball, will move, whether they desire to or not. In fact, though only a small portion of the conversation can be seen, HS 4505 (in one panel) we see Aradia conversing with via Trollian, highlighting a portion of his text that suggests he doesn't understand the arrival of Jack Noir to the trolls' incipisphere, and isn't supposed to be involved with this particular incident. When he speaks to Vriska it is with an air of superiority, telling Vriska that "The short amount of time I have reserved for arguing with a child has expired."

He has a soft spot for young ladies, HS 5527 (as mentioned here), though not in the way one would immediately assume. So far, besides brief conversations with Karkat and Gamzee, all the children he's contacted have been female, and he generally tries to be as civil and polite as possible to them whilst manipulating them. This can sometimes become awkward, as seen in the previous link, though likely makes it purposefully so for his own amusement.

Being near omniscient, anything unexpected or unexplainable is very troubling for him. For example, Vriska had been able to inch closer to victory during their matches of what appeared to be chess on a game board that looks exactly like the Skaian battlefield after receiving the second Kernelsprite. In addition Terezi had been able to initiate contact with him, despite lacking an account name, an internet connection, and a computer, through the help of Sollux. He refused to tell her his name and instead told her to call him Mr. Vanilla Milkshake, foreshadowing Terezi's future habit of associating colors with flavors. Terezi then explained to him that the only reason Vriska was winning in their games was because she was cheating by using one of 's lost Magic Cue Balls. After being informed of this, uncharacteristically HS 4163 (flips the fuck out) and blows up the Cue Ball in Vriska's face, removing her vision eightfold and her arm.

After setting all of the conditions for the summoning of, claims that he feels he has no further purpose, and has begun to yearn for his own destruction. His relationship with Rose is one part mentorship and two parts creeping her out, with Scratch teasing her and calling her cute even though it skeeves her out. Despite once saying to her [], Rose ends creating the Green Sun anyway.

Aranea states that the trolls' violent behavior is a result of 's conditioning of their race, something that did not happen in her timeline.

Similarities to components
Because is Lil Cal's genetic son, he is genetically composed of the combination of Caliborn, Gamzee, Equius, and Auto-Responder/Lil Hal's traits. Given that Doc Scratch is omniscient, he is most likely aware of this.

The way he speaks and his personality reflects each of his components. His self-assuredness, his laugh, the clothing, and his repetitive and intricate manner of speech reflects Caliborn; his calm demeanor and bowls of candy reflects Gamzee; his perfect grammar and speaking style mimics AR/Lil Hal; and his strength, formality, and refusal to swear reflects Equius.

Trivia

 * As of HS 5664 (this update), you can view any adventure before HS 5982 (SNOP) with a . The candy-corn top-border dividers are replaced with cue balls, the ads are replaced with an image of his room in Manor, the MS Paint Adventures logo is replaced with a cue ball, and the entire screen is shown in green. Clicking  Manor image or the cue ball will revert it to normality.
 * As of HS 5697 (this update) himself now appears in the top banner, after claiming he will "step away for a moment" from his task of telling the story directly. As the pages progress in the main story, the scene on the top banner plays out HS 5514 (this update), and scenes preceding and succeeding it. Spades Slick pours oil over all over 's study, while  is "distacted" with the narration. In the banner of HS 5722 (this update), in the light of the fire, Hella Jeff's face is visible in or on 's head.
 * Hussie continues using this format for dual-storytelling purposes until HS 5982 (this page).
 * Even though the Trollian background is white and the trolls HS 4145 (need to highlight his text) to be able to read it, the text is slightly whiter than the site's light grey background, and as such, readable on some screens.
 * According to the alt text of the top banner of HS 5972 (this update), is four feet tall, making him the only character with a canonical height.
 * With the introduction of the God Cat in the post-Scratch kids' world, it is implied that there was a different guardian in the pre-Scratch trolls' session. Who this guardian was, or whether they existed is unknown.
 * The green moon where lives did HS 6678 (not exist) in the pre-Scratch troll universe. Because of this, it is likely that  created or brought the moon to Alternia from somewhere else to use as his home.
 * A holster identical to 's can be seen hanging in Calliope's room, and she wields a gun very similar to his white magnum. As is later seen with a wand very similar to its weapon's innocuous double, using it to kill dream bubble ghosts, it is possible that it is in fact the same holster. Order of ownership however is thus far unknown due to possibility of Gamzee-related temporal tampering.
 * The wolf HS 4393 (that harasses) Hussie in HS 5963 ('s apartment) is Gmork from The Neverending Story.
 * is depicted holding the broom used to reprimand the Handmaid on the "I: The Magician" card in the Homestuck Tarot Card Deck. He is also on the "Ten of Wands" card.
 * The genetic codes used to create relate to HS 6011 ('s summoning). The   code represents the  of 's grandfather clock present in the flash, the   code represents 's cue ball , and the  code represents the Vast.
 * Since Arquiusprite is part of him, he can be seen as HS 9348 (Rose's literal uncle), a familial title he once suggested she call himHS 5527.