Bloodswapping is a trope in which writers change the color of the trolls’ blood. This hemospectrum of twelve colors is directly linked to a caste system on Alternia, the trolls’ planet, in which the color of one’s blood decides his/her position on the social ladder. Bloodswapping was popularized by the August 2011 fanfic Castelocked, in which the typically yellow-blooded Sollux chooses to hide his color, similar to Karkat in the original story, and the low-class bronze-blooded Tavros is royalty. Bloodswapping is a popular trope in fan art on Tumblr and deviantArt.
In Homestuck, a Lusus Naturae (or a Custodian) is a large animal, colored entirely in white, who looks after a young troll. Each of the twelve main troll characters has a Lusus.
In Guidestuck, these Lusii become trolls that message Quinn, Jaspers, Cal and Bec, and the trolls become their Lusii.
Ocerus / poseidonsCoronation
Often roleplays with Quinn, where she pretends she's Princess Quianna and he pretends he's a merman named Otto. Cal is also into this game, as Princess Calypso. He types in Eridan's color, and adds a tilde after each v and before each w.
Participates in a long conversation with Jaspers, warning him not to fuck up the prototyping process which created Jadepuppysprite. Needless to say, Jaspers fucks up anyway. He types in black, uses no quirk apart from the lack of periods, and "chides" people instead of "trolling" them.
Wyvern / twistedAcquittal
First Lusus to appear in Guidestuck. She messages Bec, warning him not to play Sburb Omega, however, she fails and realizes the timeline is doomed. She uses Terezi's typing quirk and color.
Stheno / gorgonsTemptation
Referred to by brokenCaballus as Lady Serket. Replaces s with §. Associates with Bec.
Aurthour / brokenCaballus
Replaces o with O->. Calls all his fellow Lusii "Misters and Misses". Associates with Quinn.
Cappra / archaeologicalGrifter
Replaces a with @, uses sheep puns. Replaces all "you" and similar sounds with ewe. Associates with Jaspers.
Types in Gamzee's purple. Only puts ★STARS★ around his nouns. Capitalizes only the word "I". Also emphasizes by repeating letters. Lacks punctuation anything further than a apostrophes, often contracts or abbreviates ("sayin", "I'ma", "wanna") words. Has the tendency to say "nehhh", the number of each letter varying according on his distaste. Uses e v e and e ^ e emoticons.
Types in gray and in ALL CAPS. Begins and ends each line with a "(\ /)" symbol, followed (or preceded at the end of the line) by an exclamation mark (\ /) ! LIKE THIS ! (\ /) to represent a crab's pincers and stalks. He is overly dramatic and apologetic. He is the latest lusus introduced, last seen trying to help Quinn.
A story involving the ancetors as younger versions of themselves.