Lrd English is an indestructible demon summoned at the end of the universe, although his time travel abilities allow him to appear prior to his actual summoning. He apparently cannot be destroyed by ordinary means, but only through the exploitation of a number of time-based glitches and loopholes. He is the leader of The Felt on Alternia, and his appearance resembles that of a cherub, in particular Caliborn.
Physically, English seems to be a hulking, veined dark green cherub with clawed appendages, a pool cue for one leg and a head that bears more than a passing resemblance to that of Lil' Cal, except skeletal and fanged. When his leg was severed during the second intermission he was shown to have candy red blood. He is said to be very, very powerful and seems to at least have some First Guardian abilities carried over from his host Doc Scratch, such as the teleportation of his coat.
English owns a Cairo Overcoat (an obvious mirror to Mobster Kingpin's Chicago Overcoat) that represents the spacetime continuum and gets damaged when time-related things get out of hand, and a Backup Coat, that may or may not possess the same qualities. The Cairo Overcoat can turn into an Egyptian sarcophagus, which English can entomb himself in in order to travel throughout time once inside a universe. More recently, English has been shown to have in his possession a golden scepter, atop which is an orb, glowing with multiple colors, that possibly represents the Green Sun. This scepter seemingly demonstrates a more controlled form of Weapon/Object Duality, as it has been shown to morph into a golden assault rifle. Andrew Hussie met his end by this transforming scepter.
Sollux held a code that cycled through pictures of pool balls, oddly specific considering the presence of The Felt within the Troll's universe. The ~ATH code was copied from an obscure server far beyond the planet's global network and is completely unhackable. The code is said to summon an indestructible demon, who can travel freely through time, once the universe has been destroyed. Seeing as the demon can travel through time, it is actually already here, making the virus essentially a formality. The demon is none other than English himself; the code, when activated, causes English to emerge from the body of his host, Doc Scratch.
English has never known any form of defeat. In addition to his indestructibility, multiple incarnations of him exist simultaneously in multiple universes, making it virtually impossible to permanently end his existence. Despite these overwhelming factors, Aranea believes that Jake is destined to best English in combat, which would mark the demon's first defeat and send hope to others that one day he may be destroyed forever.
Biography
(Note: Since it's difficult to know the chronological sequence of English's actions throughout the story, the following events are written in the order they appear in the comic.)
The Midnight Crew Intermission introduced English as the leader of The Felt. Spades Slick attempted to pry open English's vault with Crowbar's crowbar, which transported him to a timeline where everyone except him, Snowman, and presumably English were dead.
During Rose and Dave's chat in which she reveals her plan to use her dream self to destroy the Green Sun, Rose mentions that she had help thinking up the plan from Scratch, who says he successfully completed everything that English required from him. Scratch also mentions that his death is required for English's arrival, and that throughout the countless universes in which instances of him have been created, he has never failed in bringing him back, and never will.
Scratch also mentions that English is a very evil man and that his name is merely a title, and not the demon's actual name. According to the narrator, to know his true name is to "understand terror no human ever has." However, there is one scene starting here in which the audience does get to see English, and he appears to be Andrew Hussie himself. However, Andrew then confirms that he is not actually English; he is only wearing his coat (which is still much too big for him).
Then, a small portion of him (his eyes) was revealed in thesethreeupdates at the top banner. At the time we could tell that English has two eyes, large clawed and green hands, and speaks in a bold green text almost similar to the Exiles. The pool balls that appear together on each frame are paired like Quarters' coins; 1 and 11, 2 and 12, 3 and 13, 4 and 14, 5 and 15, 6 and 9, 7 and 10 and finally, two eight balls. The significance of this (if any) has yet to be seen. However, 111 is an arc number for Act 6, while 6 and 9 have been used to refer to the "sym69l" of The Signless. Meanwhile, 8 is the sum of 4, 1 and 3.
When The Handmaid tries to escape from Scratch's manor, Lrd English intercepts her and takes her into his service. Later, the Handmaid enlists The Condesce to continue English's service in another universe; namely the post-scratch human session.
In Intermission 2, the ~ATH program was shown to execute after Snowman had died, destroying the Trolls' universe. Scratch's body is used to create or channel English, for as we all know, Scratch is an excellent "host". At this point, English was revealed in full. Upon his "release," he summoned his Cairo Overcoat, which then transformed into an Egyptian Sarcophagus, which closed over him and traveled back in time. He then made two loud honking sounds, an event referred to as the Vast Honk.
Interestingly, during English's summoning the parts of Scratch's genetic code that were written in the troll's Flarp rulebooks occur. The grandfather clock "t1ck"s and "t0ck"s. After which the "8r8k H34DS" occurs as Scratch's head breaks. Then English proceeds to "honk HONK".
As of this panel, English has somehow entered Andrew Hussie's home and seemingly destroyed the Hussiebot. He is seen in possession of a large scepter. It is possible that this scepter is related to the one that the Black and White Kings wield. The head of the scepter flashes multiple colors (blue, cerulean, yellow, orange, red, and gray) and is sometimes replaced with an image of the Green Sun. After giving poor Ms. Paint a CANEing with it, he proceeds to corner Hussie, turn the scepter into an assault rifle with a Green Sun sight, and messily gun our beloved author down.
Immediately after killing Hussie, English enters his sarcophagus and flies through the Furthest Ring. He lands inside a dream bubble containing the doomed timeline versions of the pre-scratch kids and post-scratch trolls. Using the White Wand, he conjures a beam of energy that bursts from his mouth, killing the doomed timeline characters and destroying the bubble in an explosion visually reminiscent of shattering glass. It is shown that this has caused harm to the Horror Terrors as one of them was shown to have a cut limb. This was witnessed by Dave possibly as a callback where he first listened to the HorrorTerrors saying to Rose that they are being killed.
Trivia
English is named after the pool term 'english', meaning spin on the cue ball (which refers to his relationship with Doc Scratch, who represents the cue ball), and retroactively also named after Ultima's Lord British, an invincible character who could only be killed through manipulation of various game mechanics in the early installments of the series (although later installments regularly allowed players to slay him through intentional easter eggs). If this reference is expanded upon, it is absolutely possible that he could lose his invincibility in the Alpha session. When Lord British died for the first time in Ultima Online, it was because a developer forgot to turn on his "invincibility flag" when carrying his character between sessions. Similarly, he could have left his invincibility "at home". His name may also be a (likely unintentional) reference to the Lord British Space Destroyer, a fighter ship of Gradius fame. His name and connection to Jake English may also have drawn inspiration from the phrase "The devil is an Englishman"
Calliope has stated that she likes the planet Uranus because of its unusual rotation compared to other planets, although she forgets (or possibly cannot utter) the technical term for it. This is again referencing the term for the spin on a ball.
English may further extend the billiards parallel as the cue stick, using Scratch, the First Guardian of Alternia, in order to affect other individuals on his field of play, and to ensure his summoning.
Hussie has confirmed the Cairo Overcoat's dual nature as being a play on mobster slang - just as a Chicago Overcoat referred to a coffin in Problem Sleuth, so would a Cairo Overcoat refer to a sarcophagus, as Cairo is a notable city near the pyramids and subsequently sarcophagi. Using a sarcophagus for time travel may also be a reference to Pharoid's time chamber.
It has been confirmed that English inspired the mirthful messiahs of Gamzee's religion, along with Scratch. He also appears to have inspired the Troll concept of Death, along with The Handmaid. This page on Andrew Hussie's tumblr contains some insightful information on English.
English harbors a connection to Jake English. Jake's shirt has the likeness of English on it, he wears computers that resemble various aspects of English's appearance, and a piece of Homestuck fan art in the form of a fake movie poster featuring English made it into Jake's Room. These are all due to his grandmother's company, designing its products to be reminiscent of English, specifically to remind the Condesce of her greatest fear. Jake's Grandma also took English as her last name to serve the same purpose which was eventually inherited by Jake.
English's head appears to look slightly like A puppet we know. This may be because Doc Scratch, his host, is ectobiologically created from said puppet and a Magic Cue Ball.
Dirk Strider may also bear a connection to English, albeit far less significant than Jake's, due to his bedspread having pool balls on it.
In the Intermission, English's name appears as Lord English, without the flashing pool ball sequence replacing the "o" in Lord. It doesn't appear until Doc Scratch's introduction in Act 5 Act 1.
English may be a future form of Caliborn, as indicated by his lost leg and previously missing tooth as well as their similar weaponry. It should also be noted that English was seen in front of a red Quest Bed with the Time symbol on it. Caliborn is a player of time in his session, therefore it may be possible that English is a fully-realized god tier time player of the currently unknown male master class (Suspected to actually be the Lord (which may be why Calliope does not dare to say what Caliborn's class is)).
Or, similar to Vriska having sustaining the same injuries as her ancestor, the similarity in injuries between English and Caliborn may point to English being Caliborn's ancestor/guardian/Cherub version of the two.
The spiral pattern found on Calliope/Caliborn's cheeks appears behind him, albeit in flashing colors, prior to the destruction of the Dream Bubble.
Gallery
English's CAIRO OVERCOAT
unhackable.~ath, the code that summons English
The server that contains the code that summons English
The Cairo Overcoat.
The banner that first showed English's flashing, pool ball eyes.
English releases a Vast Honk.
Rose learns about Lrd English.
A clear view of English's head by Hussie.
English looming over Ms. Paint.
English striking Ms. Paint. Note that his scepter resembles a pool cue.
English gets more terrifying with every new view of his face.
The less innocuous double of the already not-very-innocuous staff.
The poster in Jake English's room.
Lrd English floats past the remaining unopened sub-acts of Act 6.