The order in which the ghosts are placed on the zodiac seems to be based on how dangerous they are (with the exception of The First Born Son, who is threatening, regardless of being the first ghost, while the next three seem benign, or at the very least unable to do any damage).
There are thirteen souls bound to earth, foretold and described in The Arcanum, which make up the Black Zodiac, as follows:
The first ghost in the Black Zodiac. The First Born Son is the ghost of a little boy who dies of a shot through the head or some other form of head injury. It may possibly also represent an infant ghost or a firstborn, male child. Cyrus chose the ghost of Billy Michaels as the First Born Son.
The second ghost in the Black Zodiac. The Torso is missing his legs, and/or his waist, it possibly represents a severed or mutilated ghost . Cyrus chose the ghost of Jimmy Gambino as the Torso.
The third ghost in the Black Zodiac. This ghost is of a woman who died having been tied-up in some fashion, but in the Arcanum, the only bound ghost is the Angry Princess (in which case, it just represents general suicide), so it is entirely possible that instead of being physically bound, this ghost had, as a prerequisite, sealed her own fate, as seen by how her infidelity led to her demise. Cyrus chose the ghost of Susan LeGrow as the Bound Woman.
The fourth ghost in the Black Zodiac. This ghost is of someone who died having a withered or worn appearance, it may also represent someone (the prerequisite may be that of a woman) who had her future, dreams, or relationship, destroyed or broken, like being separeted from one's mate. Cyrus chose the ghost of his niece-in-law, Jean Kriticos, as the Withered Lover.
The fifth ghost in the Black Zodiac. This ghost has much of the skin on the right side of his body missing, leaving the bones and muscles exposed, it possibly represents a "prince" (spoiled, popular, loved, etc), who's pride was taken down, or had his ego destroyed, (hence the "fallen hero" statement seen in his story). Cyrus chose the ghost of Royce Clayton as the Torn Prince.
The sixth ghost in the Black Zodiac. This ghost apparently is of a young woman who dies by committing suicide, and, as the name suggests, is that of a woman, either popular, spoiled or beatiful (just like a princess) that couldn't see past her privileges, and, as such, she would be unhappy with her blessings. Cyrus chose the ghost of Dana Newman as the Angry Princess.
The seventh ghost in the Black Zodiac. It appears to be the ghost of a female pilgrim or a primitive woman, it may also represent an outsider or stranger, not appreciated by the town, seeing the implications of her alien origins. Cyrus chose the ghost of Isabella Smith as the Pilgrimess.
The eighth and ninth ghosts in the Black Zodiac. The Great Child is the ghost of a very large and overweight child, and the Dire Mother is that of a very small stature, they probably are ghosts of a child, spoiled even to its maturity, and a mother bad enough to let it happen. They may also be the ghosts of related mother and child. Cyrus chose the ghosts of Harold and Margaret Shelburne as the Great Child and the Dire Mother.
The tenth ghost in the Black Zodiac. This ghost is that of a muscular, heavy-set blacksmith who wields a large hammer, further or deeper implications are unkown. Cyrus chose the ghost of George Markley as the Hammer.
The eleventh ghost in the Black Zodiac. The Jackal is the ghost of a dishevelled man wearing a cage on his head, which probably represents bestiality or wildness, seen as how much of a savage and of how aggressive the ghost is, as well as his depraved sexual implications. Cyrus chose the ghost of Ryan Kuhn as the Jackal.
The twelfth ghost in the Black Zodiac. This ghost is that of a tall, ugly and incredibly-strong man. Cyrus chose the ghost of Horace Mahoney as the Juggernaut.
The thirteenth and final ghost in the Black Zodiac. This ghost dies by leaping into the core of Basileus's Machine out of an act of pure love. Cyrus chose his nephew, Arthur Kriticos as the Broken Heart.