Mythological roles

Each of the Homestuck Kids and the Trolls has a mythological role, as hinted at, during various points of the Homestuck story. All titles appear to consist of two components - a "class" and an "aspect." A title can be assembled from any combination of class and aspect - John in the kids' session is the Heir of Breath, while in the Trolls' session Tavros is the Page of Breath and Equius is the Heir of Void.

The term "HS 5528 (Hero)" can be used in lieu of the class when the speaker wishes to be generic, ie: John and Tavros are "Heroes of Breath". Both components of the title appear to have some mechanical effect on the game, although the precise nature of these mechanics has yet to be revealed, except for HS 5733 (two).

It appears Sburb may design planets with the titles in mind, as well as a secondary theme. The planets in the kids' session relate to their elements and associated items, and the ones in the Trolls' session relate to their personal interests.

uranianUmbra reveals to Roxy Lalonde that there are passive classes (+) and active classes (-); "HS 6414 (active classes exploit their aspect to benefit themselves, while passive classes allow their aspect to benefit others)". The example she gives is the dichotomy between the Rogue, a passive class, and a Thief, an active class, whose are both heroes who steal. A Thief steals to benefit herself, while a Rogue steals to benefit her party members. UU also explains that some of the classes tend to be assigned to males or females, while others are always male or always female. She also adds that heroes with different aspects can end up with similar powers depending on their class; the Life and Doom aspects may be radically different, but depending on if the class is passive or active their powers may end up being the same.

Alternate Future Dave HS 03543 (said) that the game could not be finished with a dead Heir nor Witch, so these roles may be vital to completing the game, but this could have meant that the game cannot be beaten with any of the players dead. implies that every session will have a Hero of Time, and if the breeding duties are indeed linked to the Hero of Space they would be another constant in the game. Apart from this, the mechanical functions of the classes are unknown.

Classes

 * The Seer class fills one of the support roles in-game. True Seers, according to Word of, would not charge into the fray headlong but direct it as a conductor with a baton. They would sift through an infinitely-splitting mental map of every possible mistake made by their teammates and themselves, easily uncovering any gambits or malevolent desires and even imminent defeat due to a single grossly miscalculated and instinctive action as if they had the Official Prima Strategy Guide for Sburb imprinted deep in their mind.
 * The Knight class, as the name implies, serves as a protector for other players in the session. Dave (The Knight of Time) has so far saved the lives of every member of his team, such as resetting the timeline to save John and Jade, and rescuing Rose from the Draconian Dignitary near the end of act five (though whether she actually needed the help is debatable). Karkat (The Knight of Blood) is less successful in the role despite his best efforts, as he is very ineffective at protecting the unconscious Sollux during Gamzee's rampage. He does, however, manage to diffuse the HS 005985 (Rare and Highly Dangerous 5x Showdown Combo), which would have doubtlessly killed one or more of his surviving friends.
 * The Knight may also have something to do with breeding the genesis frog, since in both sessions so far, the Knight has assisted the Hero of Space in the breeding - Karkat (the Knight of Blood) assisted Kanaya, and Dave (the Knight of Time) assisted Jade. However, this may be coincidence without correlation.
 * The Thief class is fairly self-explanatory. Vriska, as the Thief of Light, is able to steal luck (or fortune) from her allies or enemies, thereby making herself luckier. Thieves of other aspects would likely act similarly, turning the power of others against them. It is an "active" class, in comparison with its passive counterpart the Rogue, which means that a Thief is mainly benefitting his or her own needs. Thief is a class generally assigned to female players.
 * The Rogue class is the passive version counterpart of the Thief class. While a Thief will steal things to benefit herself, the Rogue will steal things to benefit others. When explained the dichotomy between the passive and active classes, Roxy Lalonde determines that she is the "Robin Hood of Void". Rogue is a class generally assigned to female players.
 * The Witch seems to be a manipulator of her unique aspect. For example, the Condesce (and presumably Feferi Peixes) could manipulate the life force of others and extend their lives to match her own, whereas Jade Harley is able to move objects, people, and even planets to other locations instantly, as well as resizing them to her own will. Whether or not this is due to her fusion with Becquerel is debatable.
 * The Witch and Mage may be the same type of class, simply distinctualized by gender, or be active / passive counterparts to each other. Another possibility, suggested by Jade's conversation with Kanaya, about their titles is that the Witch and Sylph classes may be passive / active counterparts. According to Kanaya, she thinks a Sylph is like a "magical witch".
 * The Prince class is a destroyer class. It is an "active" class in comparison to it's passive counterpart the Bard. Prince is a male exclusive class.

Aspects

 * The Breath aspect seems to have some relationship to John's power over wind (such as The Windy Thing). It was never revealed whether Tavros has or could have had equivalent powers, but since he spent most of his time in the game asleep or otherwise passive, it seems unlikely that he was able to complete whatever makes those powers available. However, as shown HS 5003 (here), Tavros's breath appears as blue lines similar to the Breath symbol. The significance of this is currently unknown. The associated Denizen of the Breath aspect is Typheus, who presumably fills the role for all Breath players.
 * The Light aspect is equivalent to "fortune", and involves power over luck. At some point during their lives, both Vriska and Rose have the ability to see through solid objects, although Vriska's ability may be part of her troll biology, and Rose's power may be related to her role as a Seer. It has been speculated that Rose did not literally see through the magic cue ball, but that the scene was merely a visual representation of her prediction of the roll of the die contained within using her presumed "luck prediction" powers. The associated Denizen of the Light aspect is Cetus, who accordingly fills the role for all Light players.
 * The Time aspect is associated with the Timetables, time travel, and timeline maintenance in general. Heroes of Time are able to influence time without the use of timetables (or time music boxes), just as all players eventually learn that their powers are not dependent upon their alchemized equipment and that such props were never required. The player of Time also has a feature installed in their personal world in the incipisphere: a large structure that will obliterate the alpha and alternate timelines to rewind everything to before the game starts, as an attempt to have better starting conditions. The associated Denizen of the Time aspect is Hephaestus, who presumably fills the role for all Time players.
 * The Space aspect is associated with the player whose World contains their session's Forge. Both Kanaya and Jade live in Similar homes, next to a Frog Temple, and their dream selves are both awake before entering the session. Having their planet's First Guardian as a guardian is also a parallel (Jade was effectively raised by Bec while Kanaya was doc scratch's "protégé"), although Kanaya also had her Lusus for the majority of her life, and Jade's Grandpa died when she was still an infant. Beyond this, both players of Space have been in charge of the breeding of the genesis frog. How many of these similarities are coincidences and how many relate to the space aspect is anyone's guess. The associated Denizen of the Space aspect is Echidna, who accordingly fills the role for all Space players.
 * The Mind aspect is as yet associated with only one player, who also happens to be a seer. In this role, the Mind aspect's powers take the form of literally envisioning the aforementioned mental map of alternative possibilities (see Seer, above) manifesting as an HS 5734 (infinite net of flashing, teal synapses with images of each possibility inside each synapse). Even before playing sgrub, Terezi possessed the ability to manipulate and understand others, bending them to their will, although, this being paradox space, a causal relationship between this ability and her role as the Seer of Mind is impossible to establish and, as the two are ultimately indistinguishable, is something of a moot point.
 * From evidence presented in HS 6308 (this page), it would seem likely that the Life aspect is associated with an ability to heal oneself, and possibly others too. Given the reference to health stats in many videogames as 'life' and the measures available to replenish it, it would make sense that there can exist within Sburb some capacity to restore health (other than Vitality Gel). In this case, it may take the form of a player with restorative abilities. It would also seem to fit the general attitude of at least one of the players known to possess this aspect, as she so often champions "caring for the fit and unfirm". It would also seem to fit the story of her ancestor too, who had both a centuries-long lifespan and seemingly, an HS 5960 (ability to share it). More on Life powers will be probably be clarified soon when we see what has happened to the Dream Self of the other player known to possess Life powers who, after being stabbed and confirmed dead, was engulfed in a burst of blue energy displaying the Life emblem, the consequences of which remain unknown.
 * The Void is associated with "the essence of lack, or nothingness" and "the obfuscation of knowledge, or its outright destruction". It seems to enable players to act without being seen or noticed, as evinced by Darkleer's apparent ability to hide the Cue Ball from, Equius' similar talents during Vriska's struggles with the omniscient ballhead, and Roxy's occasional "dark patches" from the viewpoint of uranianUmbra.
 * According to Hussie's Tumblr questionnaires, the aspect of Rage is associated with fear and nightmares, which would explain how most other trolls were unable to oppose Gamzee directly during his rampage.
 * While the aspect of Blood hasn't been dwelled upon, it's rather interesting that the one person the Knight of Blood tried to revive subsequently rose as a vampire rainbow drinker...

Speculation
In HS 4467 (one of Karkat's memos), Kanaya speculates that Skaia assigns titles to players to challenge them, rather than to suit their strengths. This would certainly explain some of the apparent inversions, such as Rose being the Seer of Light despite her fascination with darkness and horror, and Jade's title as the Witch of Space despite her life never leaving her small island. However, her theory should be taken with a grain of salt, considering the titles of a lot of the players match them perfectly. It could be speculated that players are meant to "grow into" their roles; that is, when they first begin the session their title and its duties force them outside their comfort zone and seem very unsuited, but a fully realized Hero has matured into the role the game has assigned them.

Trivia
According to Andrew Hussie, other characters have also assumed these titles, or otherwise will when they ascend to the God Tiers.


 * Nicolas Cage is the Nick of Time
 * fedorafreak is the Gent of Piss
 * Andrew Hussie is the Huss of Lips
 * And, simultaneously, the Waste of Space.
 * Along with the Destroyer of Ships.
 * Alternatively, the Thief of Life.

In Problem Sleuth, Problem Sleuth obtains the title PS 1760 (CHAMPION OF PULCHRITUDE) by saving a universe. It is the only known mythological role outside of Homestuck.