Zodiac

The zodiac is a concept in astrology, where a number of signs relating to constellations have influence on the world. The concept of the zodiac, and in particular the western one, features prominently in Homestuck, most notably through the trolls, and is also connected to the cherubs.

The twelve signs of the western zodiac on Earth are represented by the same symbols appearing on the shirts of the twelve trolls who created Universe B, and it would appear that due to the influence of these trolls (or at least, not coincidentally) the western zodiac's signs represent various traits of theirs.

Alternia is stated to have HS 4475 (48 signs) in its own zodiac, which are independent of the symbols appearing on the trolls' shirts, as these symbols are said to be derived from HS 5374 (their caste). On Alternia, each member of a given caste is to be labeled with one symbol derived from an alphabet used for that caste, after their hatching. The symbol for Cancer is specifically derived from HS 5956 (a method of execution). Andrew Hussie has joked that the trolls have 48 zodiac signs because of the 48 squiddles that created their universe. It may be worth noting however that Ptolemy in his categorization of the constellations listed 48 constellations.

Zodiac signs
On November 27, 2017, an extended zodiac which includes the Hiveswap troll's symbols was released along with an official symbol test based on your Lunar Sway and the twelve Sburb aspects.

13th and 14th signs
In 1970, Stephen Schmidt suggested the addition of two more signs, Ophiuchus and Cetus, while this suggestion didn't catch on, in 1995 a 13 sign system only adding Ophiuchus to the tradition twelve was suggested by Walter Berg and Mark Yazaki. The 13-sign system has gained traction and as such when the original twelve trolls were introduced many suspected a 13th troll to exist. Eventually the character of Calliope was introduced who initially appeared to be a new troll appeared who used a Caduceus as their symbol. While not a constellation in itself, both it and Ophiuchus are connected to snakes. Later still, Calliope's brother, Caliborn, who used the exact symbol for Ophiuchus was introduced. The characters were later revealed to not have been trolls, but rather cherubs, a species having serpentine features, and also shared a singular body. A semi-canon thirteenth troll exists in Paradox Space, although his symbol is not related to any constellation at all.
 * Ophiuchus (⛎) - The sign of Caliborn.
 * Cetus - No character uses this sign, however the sign is named after a mythological monster of the same name that appears in Homestuck as a denizen.