Troll

An internet troll is someone who willingly harasses other people on the internet. They are often times hackers, breaking into someones profile and defacing it.

In Homestuck, there is a group of twelve trolls who often bother the kids on Pesterchum. They live on another planet at an unknown point in the future. They are humanoid, and appear to be children the same age as the protagonists. They have grey skin, yellow sunken eyes, pointed teeth and black hair. Each one wears a shirt depicting his or her associated zodiac sign. Their most noticeable features are the horns sprouting from their heads, which resemble Candy Corn. Each troll’s horns appear to reflect that trolls’ zodiac sign; for example, GC’s (♎) horns are pointed to a tip and nearly horizontal, while Karkat’s (♋) are curved and rounded, AT's (♉) are massive like a bull's, and TA has two pairs.

They have completed their Sburb session as a chain of 12 players, and now reside in The Veil, where they use their equipment to talk to the kids at any point in the timeline, even months before the story began. They appear to be trolling the kids out of anger. According to this conversation between John and Karkat, in Karkat's timeline the Homestuck kids have already lost, and not only that... they have 'screwed up' the game so badly that apparantly all the trolls are going to die (according to twinArmageddons). There is speculation that this 'screw up' begins with Jade's present to John ending up on the desk of one Jack Noir, who consequently uses it to slay the Black Queen. It was given to the Parcel Mistress when she gave Jack Noir the white king and queen's crowns after "deposing" both. (He uses the sword from his chest when he murders the Black King in-between).

Homestuck has introduced five of them. They've been pestering Jade Harley for years now, and have even forced John to change his PesterChum handle. One of them seems to have befriended Rose, who may even be giving them trolling tips. Two of the five trolls we have seen are very bad at trolling, with adiosToreador becoming so freaked out with Dave's sick fantasies ill beats that he blocks Dave, rather than the other way around. Karkat tells John that the trolls will, in the kids' future, inadvertently form a sort of friendship with the kids.

The trolls have names tied to the Greek Zodiac. Adding their abbreviated chumhandles to GG, GT, TG, and TT makes the 16 possible two-letter names from the letters A, C, G, and T, the four nucleotides of DNA.

Speculation
It's possible that the trolls are somehow connected to the kids as counterparts or 'evil twins.' A few of them exhibit traits that are the reverse of traits the kids have (i.e. adiosToreador, a possible counterpart to Dave, is very weak-willed and under-confident). Others have 'corrupted' versions of traits the kids have. For example, gallowsCalibrator, who looks a lot like Jade, takes Jade's silliness to a manic level and has a beast-like sense of smell.

Unencountered Trolls
Several of the trolls not yet seen on screen have been described by the active trolls. GC refers to these other trolls as "not that enthusaistic about trolling" the cast. It is possible that these characters will remain off screen and off Pesterchum for as long as possible so that Andrew can save himself the trouble of drawing them and coming up with individual new ways to abuse the English language. The traits of these semi-known trolls are listed below.
 * A female troll that is "in charge of the timeline management".
 * A troll whose only shown feature thus far is his/her pincer-like horn. This is possibly ArachnidsGrip, as his/her sign is Scorpio (or CuttlefishCuller, as the symbol for Pisces strongly resembles the horns).
 * There is some speculation about another troll, using the little-known Zodiac sign Ophiuchus, also known as Serpentarius. However, due to the DNA naming system, there are no more available chumhandles.
 * Four troll Titles have been revealed, which may or may not correspond to trolls we have actually encountered: Seer of Mind, Maid of Time, Knight of Blood, and Page of Breath.
 * It's possible that the Maid of Time is the one responsible for timeline management.
 * Possibly Jade's penpal, who uses green text, only capitalizes the first letter in a sentence, then uses no puncuation, except to end the sentence. Note that the text color is the same as Jade's.