Alterniabound

Alterniabound, titled in Homestuck as HS 4692 ([S] Past Karkat: Wake up), is an interactive Flash segment in Act 5 Act 2, posted on 10/25/10, starring the trolls in their Ectobiology Lab in the Veil, soon after their first contact with the kids. Its name is based on the video game EarthBound.

In this game, you play as Karkat, Terezi, and Vriska as they search through the lab, examining objects of interest and collecting items from treasure chests (although none of the objects do anything apart from getting a humorous reaction/description from the character).

There is a complete transcript of the text in this segment on.

Main Room and Hub
The Flash starts off with Karkat awakening in the main computer room in the lab aboard the meteor. As Karkat you can use a computer to HS 4467 (finish an earlier memo with Kanaya) and talk to the other 11 trolls about the recently discovered humans, the recent destruction of Prospit, and "the demon" who Karkat saw while sleeping, and recognised, although he refuses to share his suspicions until he is sure of the demon's identity. While playing as Karkat you can also attempt to be future Aradia and future Feferi, these fail however as future Aradia has HS 5086 (blown up) and future Feferi is asleep on Gamzee's horn pile. You can also switch between playing as him, Terezi and Vriska.

As Vriska you can talk to the other trolls about various topics, however many of them just express discomfort about being around her. While playing as Vriska you can also briefly be future Eridan, soon after Rose HS 4706 (blew up his computer), he talks to Vriska about this, and she mocks him for allegedly having black feelings for her.

As Terezi you can talk to the other trolls about various topics, mostly the kids, how the trolls have their favourite ones and they may be the cause and solution to their current situation, however talking to Tavros will cause him to exit the room and fall down some stairs. While playing as Terezi you can also briefly be future Kanaya, sometime after Aradia has exploded, who asks Karkat what he knows of the Green Sun, however he is ignorant of it and only knows it factors into the kids' plan to kill Jack Noir.

Leaving via transportaliser at the center of the room leads to a smaller room with three transportalisers; the one you enter in on which leads back to the main room, another at the bottom end of the room leading to a carapacian lab and one to the top which leads to a hub of transportalisers leading to individual areas for each troll.

Carapacian lab
Taking the transportaliser from the bottom of the room with the transportaliser back to the main room leads to a stairwell which leads down to a lab that appears to have been use by carapacians to clone more pieces for their armies on the Battlefield. If Terezi has talked to Tavros in the computer room he can be found halfway down the stairwell. When talking to him he will proclaim that he had been warned about the stairs. Most of the tubes in the lab appear to be full of regular pawns, however three large carapacians appear to resemble a bishop, knight and rook. A transportaliser in the lab leads back to the main computer room.

Karkat's Section
Karkat's section consists of two rooms. The first room is a long hallway, lined with many chests and interrupted by stairs. At the end of the hall, next to a transportaliser, the last wall indentation contains a switch that opens a passage to a secret room halfway through the hall. The secret room contains Kanaya's dresses, some of Sollux's beehive mainframes and Horsaroni. Taking the transportaliser at the end of the hallway leads to the lab where Karkat preformed the troll ectobiology, in this room you can briefly be past Karkat just after he creates the trolls as grubs using ectobiology. The room contains 24 slime tubes as opposed to the expected 12 tubes. This scene is accessed at the center of the Ectobiology platform, where there is a sparkling point of light with which the player interacts.

Vriska's Section
Vriska's section consists of seven rooms. The first room the top of some stairs which lead to a lab which apparently monitored the Reckoning and cloned more monsters. A transportaliser leads to a hallway where Inquisiclops resides. Vriska is unable to fight it as she lacks her Fluorite Octet, so she instead kills it by stealing its luck. Reaching the end of the hall a computer is used to unlock a room full of treasure. Trying to unlock the next room behind a password encoded door allows you to become future Vriska.

As future Vriska the treasure is gone as it has been given to John to give him an edge over Dave. The final room contains a shrine to Nicolas Cage with "YEAH <3" visible below the various images of Cage. A short Flash loop is played if the wall is examined.

Terezi's Section
Terezi's section consists of seven rooms. The first room consists of a long winding stair case with three apparently unreachable platforms, at the top of the stairs there is a transportaliser to the second room. The second room requires you to move a bunch of tubes onto tiles to unlock the door to the third room. The third room has a computer which opens the doors to three smaller rooms each containing a transportaliser to the previously unreachable platforms in the first room. Towards the end of the third room you pass a drawing of His Honorable Tyranny and an open chest before reaching another transportaliser which leads to the roof. On the roof Terezi's smelloscope is set up allow you to smell the aftermath of the destruction of Prospit, after which a nearby chest opens which allows you to become future Terezi.

As future Terezi opening the chest causes you to don a Dragonsuit and begin roleplaying as a Legislascerator who is solving the murder of Senator Lemonsnout, examining the smelloscope also reveals the recent destruction of Derse. Leaving the roof, the previously open chest now contains some SBAHJ art, and a drawing of Dave and Terezi together is now on the walls, and His Tyranny has been altered to be more SBAHJ-ish. Heading back to the transportaliser hub, Nepeta can be found, roleplaying as the Pouncellor, she leads you to the secret room where Eridan's pile of wands are located and tells you that you are free to borrow it but informs you the ban on napping is still in place and has been expanded to include Derse dreamers. Sleeping in the pile causes the game to end, this game over has no real meaning as explained.

Information of Note

 * Gamzee tries to charge the other trolls to sleep in his horn pile (420 Boondollars or a pinch of magic star dust). He dances in a bizarre fashion - actually the same manner of movement as shopkeepers in the game Secret of Mana.
 * All of the trolls' Sprites have died, except Aradia.

Common areas
Hub Stairwell Cloning Lab
 * Some Boondollars
 * The trusty Clawsickle
 * A broken bow and arrow
 * A chainsaw
 * A fairy poster
 * A beautiful musclebeast nude
 * The Crosbytop
 * A broken robot part
 * Some glasses of fresh milk

Karkat's Room
Hallway/Stairs Ectobiology Lab
 * A Boonbuck
 * A ~ATH manual
 * A Tinkerbull plush
 * A whole mess of boonbucks
 * A teapot
 * A wicked elixir
 * A beautiful work of fine art
 * Homes Smell Ya Later
 * A box of Fruit Trollups (Flavor: Orange Creamsicle Colonoscolypse)
 * A pail

Vriska's Room
Top of the stairs Lab Computer room Treasure room Nicolas Cage shrine (Future Vriska)
 * A Magic 8 Ball
 * Tavros's severed legs
 * The Fiduspear
 * A fairy poster
 * The Fluorite Octet
 * A heap of Flarp manuals
 * A pair of Rocket Boots
 * A cuttlefish
 * A broken 8 ball
 * A bust of Nick Cage (swoooooooon.)
 * A wild consort

Terezi's Room
Stairwell Hallway/Art area Platform #1 Platform #2 Platform #3 Rooftop Secret wand room (Transportaliser hub)
 * Son of Lemonsnout
 * A wild consort
 * A Flarp manual
 * Your trusty drawing chalk
 * Some gift art from a cool friend (Future Terezi)
 * A Boonbuck
 * A fairy poster
 * A Music Box Time Machine
 * A Beagle Aegis
 * A pair of Rocket Wings
 * The Demonbane Ragripper
 * A gorgeous piece of fine art
 * Deuce Clubs
 * A Brainfork
 * The assassinated corpse of Liaison Pumpkinsnuffle
 * Like 13 boondollars or something
 * The Dragonsuit (Future Terezi)
 * A drawing tablet (Future Terezi)

Trickster Mode
Pressing Ctrl+Alt+T will (unless you are future Terezi wearing a dragonsuit) bring you to a sound test room with all of the songs in the Flash and many that otherwise aren't. While being brought to the room, most of Totaka's Song plays. The room itself contains the main characters of EarthBound. Leaving the room will send you back to the main room via a Chrono Trigger "Gate". Until you "reset" the code by hitting Ctrl+T again, all the Transportalizers will use the Chrono Trigger "Gate" effect instead of their usual animation.

Glitches
Some of the glitches found in Alterniabound are also present in John: Enter Village, Kanaya: Return to the core, Equius: Seek the highb100d and Seer: Descend as they are all constructed in the same way. However some glitches are exclusive to certain Flashes due to other factors such as the presence or absence of Trickster Mode.

Shared glitches

 * Either by clicking on the gamepad icon as soon as the game loads, wait for it to fully load, then clicking on the icon again; or by rapidly clicking the gamepad icon and hitting the space bar: If done right Aradia's profile will appear next to the game controls. Aradia also appears briefly if you rapidly tap the space bar in dialog scenes.
 * This glitch can also be preformed in John: Enter Village, Kanaya: Return to the core, Equius: Seek the highb100d and Seer: Descend with John, Aradia, Nepeta and God tier John's profile appearing respectively.
 * As any character, enter Trickster Mode next to another playable character (Terezi, Karkat or Vriska) as the music room is loading, tap spacebar to open up an action window for the character you were next to and select to be the character before the loading screen ends. You should teleport back to the main as the selected character, with your original character (as well as the transportalizer and horn pile) missing. The music will also be gone, but you can restore it simply by pressing "Ctrl+T". If you go back to the music room, you will see that the missing character is there in a position relative to their location in the main room when the glitch was activated, resulting in them being outside the room in stuck in the wall unless manoeuvred correctly. They can still be conversed with if you do place them in a reachable position, however doing so makes the Music Room inescapable.
 * This glitch can also be preformed in Kanaya: Return to the core however you can talk to them and still leave the music room.
 * While talking to any of the other trolls, clicking on the controller button will cause the images during to conversation to disappear and be replaced by what appears to be the image name in the form of:.
 * This glitch can also be preformed in John: Enter Village, Kanaya: Return to the core, Equius: Seek the highb100d and Seer: Descend.
 * Not strictly a secret, but try right clicking and using 'Forward' over and over.
 * Same as above, but use "Rewind."
 * Also same, but use "Play"

Exclusive glitches

 * While using the transportalizers, pressing the space bar before the appearing animation is finished will sometimes result in the troll being unable to move, while pressing it again results in being transportalized into an inescapable, empty, version of the room you were being tranportalized to. Unless you restart or activate Trickster Mode, you'll remain stuck. In addition to this, if you are in a room with stairs when this happens you will not automatically walk diagonally on them and must zig-zag to move up or down the stairs.
 * While you are Future Terezi, you can operate Aradia's teleporter. It leads back to the top of the winding staircase through the abyss.
 * As Terezi, you can slip off her stairs and get stuck by going diagonal.

Credits
Aborted Slunk (Art), Radiation (SFX and most of the music), and Gankro (Programming), among others, are to blame for destroying two separate websites on the day of the update.

Others:
 * Boy Skylark - Robert J! Lake (xfactorinfinity)
 * Hero's Growth - Jeremy Iamurri (Solatrus)
 * Phrenic Phever - Clark Powell (Plazmataz)
 * Walk Stab Walk - Erik Scheele - (Jit)
 * Horschestra - Alexander Rosetti - (Albatross Soup)

Trivia

 * In the newspost posted along with the game, Andrew claims that there is a secret secret room, but it is currently not known if this is one of the ones described above, or one that hasn't been found yet. Since he was talking about the music, he was most likely referring to the Sound Test Room, but that won't stop anyone from searching for this very secret room. It has all the secrets. All of them.