Main Characters

==== Hanse, aka Shadowspawn ====
Ethnicity: Ilsigi
Profession: burglar
Born and raised in: Sanctuary, Downwind
Author creator: Andrew J. Offutt
Description: In the main anthology, Hanse (rhymes with "dance". He's very particular about that) is 19 or 20 years old, he's not sure. A street orphan adopted by the S'danzo Moonflower, he's tough and savvy. The various TW authors, however, attach the word "needy" to his personality.
Physically he's described as having well-developed calves from walking toe-to-heel, big "guns" from rappelling up and down buildings, but is otherwise lean and lanky. He's said to have dark curly hair, and it's implied he has darker skin as well. Offutt says he based him physically after a young Lee Marvin, but one could easily see him as Indian or Persian looking. Fans are adamant about his felinity.
Hanse in detail, from the Fandom Annex
==== Illyra ====
Ethnicity: Half S'danzo by her mother Rezzel, half probably Rankan by the father she shares with Walegrin
Profession: seer
Place she calls home: Sanctuary, The Bazaar
Author creator: Lynn Abbey
Description: Married to the blacksmith Dubro, one rarely sees Illyra outside of her home in the Bazaar. Inside that home she's described as being surrounded by curtains, and like most S'danzo wears many layers of colorful skirts, some of which hide pockets. Unlike many S'danzo she has the true sight, and isn't merely cold-reading her clients. Like the S'danzo, however, her sight is dimmest when the events are closest. She does not foresee her own imminent doom.
Despite her hermitty ways, her friends include Shadowspawn, and her story intersects with nearly every other character in the series. When someone has true sight, word gets around.
==== Prince Kadakithis ====
Ethnicity: Rankan
Profession: Prince-governor
Born and raised: a Rankan royal
Author creator: Robert Lynn Asprin
First appearance: series Introduction. 
At 19, Kadakithis is sent to Sanctuary to try to govern it, but also to get him away from the palace intrigues. He's one of the younger members of the royal Vigeles family, charismatic enough to draw a following to challenge his older brothers and half-brothers for the throne, even if he's too young and inexperienced to lead such a challenge. His detractors, which include most of Sanctuary, call him "Kittycat" for his soft touch. An Enlightenment man in a dark ages world, he'd rule without torture and executions if he could. He's naive, but he plays more naive than he is. Surely it's an act. Surely he can't be that dumb.
Can he rise to his destiny? That's a tall mountain to climb.
==== Tempus ====
War Name: Riddler; Also called: Thales, The Black, Heraclitus
Ethnicity: Unknown
Profession: General, Mercenary, Cavalry Commander, Body Guard, Philosopher, Blue Star Adept, Avatar
Home: Unknown
Author Creator: Janet Morris
First Appearance: Thieves’ World 2, “Vashanka’s Minion”
Description: 6 ½ feet tall, muscular build. Dark-blond hair, blue eyes and rugged, brutal looks. His favorite clothing is armor with a leopard-skin mantle and boars-tooth helm. In battle he wields a shark-skin gripped sword that glows pinkish at the edges when his god takes an interest in his battle.
Few mortals can survive the demands of being a god’s vessel, much less that of multiple gods. Tempus is an enigma. The name he goes by is not even his true name. Only he and one other, his sister Cime, knows from whence he came, and all the clues suggest it was not the universe of Thieves’ World.
These clues suggest that Tempus was a very different person in his youth in another world. When his sister (perhaps step-sister?) begged for his help to avoid being married away to a powerful sorcerer, Tempus agreed to deflower her. For this, both he and Cime were cursed and thrust through a dimensional gate into another world. Tempus’ curse ensured that anyone he loved would spurn him, and that any who loved him would die. He is unable to sleep, only dozing on rare occasions.
To allay his curse, Tempus finally turned to the gods. He is known to have been the avatar, at least, of Vashanka and Enlil. He has an inclination towards war and storm gods, but he is never subservient to them. 
Though it may be that his curse was more self-imposed than he will allow himself to admit, being the agent of gods has given him other superhuman abilities. He is effectively immortal, at least three centuries old, and any wound heals much faster than normal, depending on the relationship he has with his god at any particular time. In combat, he is unmatched in speed, skill or ferocity, especially when his god is within him. He is a master horseman and horse-trainer, and his supernatural abilities can be passed on to his mount.
Tempus despises magic, and fights against its wielders whenever possible. However, he spent time as a Blue Star adept, and learned enough to magically disguise himself when needed.
Tempus is thought, by the people of Thieves’ World, to come from Azehur. He was instrumental in the wars that made Ranke an empire, as well as the wars against the Nisibisi witches and warlocks on WizardWall.
He was the founder of the notorious Rankan 3rd Commando unit, and became leader of the Sacred Band of Stepsons when the warrior-priest, Abarsis, sacrificed himself to bring Tempus back into the fold. Tempus was introduced in “Vashanka’s Minion”, when he was sent by a Rankan faction to evaluate the suitability of Kadakithis, the governor of Sanctuary, for elevation to emperor.
It is implied that he has fathered many children, often through religious ritual, but three stand out: Kama, a daughter whose fighting skill earned her a place among the 3rd Commando; a son, Gyskouras, conceived in a rite to Vashanka; and a son, Cyrus, born to his sometimes-consort, Jihan, the daughter of the god, Stormbringer.
Another fan's perspective
Wikipedia article on Tempus and the Stepsons
"Interview" with Tempus at Goodreads contains spoilers
==== Hakiem ====
Ethnicity: Ilsigi
Profession: Storyteller
Home: Sanctuary
Author creator: Robert Lynn Asprin
Home: Sanctuary, emphatically
Hakiem is a homely-looking man, the kind of guy you'd mistake for old and rundown even in his youth. He opens the story of Thieves' World as a beggar in the streets, and closes the story of the Rankan era by accepting a royal position in Beysa. Yet throughout he remains comfortingly consistent, the man who listens, spins tales of what he heard, and then enjoys a drink with his earnings. 
==== Molin "Torchholder" Vigeles ====
Ethnicity: Rankan and Nisibisi
Profession: Magician, soldier, statesman, priest, architect
Home: Sanctuary, dammit
Author creator: Lynn Abbey
One of very few characters to span both the first generation books and the second, Molin is a survivor, meaning that despite his royal roots he is ultimately a Sanctan. He is powerful but entangled, moral but treacherous. If the city is your cause you could have no better ally. Anyone else needs to watch their back.
==== Walegrin ====
Ethnicity: Rankan and S'danzo
Profession: Soldier, guardsman
Home: Sanctuary?
Author creator: Lynn Abbey
Half-brother to Illyra, by their father
==== Jubal ====
Ethnicity: unknown, but said to have dark black skin
Profession: Crime lord, slave trader
Home: the Maze
Author creator: Robert Lynn Asprin
==== Lythande ====
Ethnicity:
Profession: Wizard (Blue Star Adept)
Home:
Author/creator: Marion Zimmer Bradley
Lythande is a wizard with a secret, a secret that if discovered would take away their hard-earned magic powers. 
==== Ischade ====
Ethnicity: ...
Profession: Magic
Home: by the White Foal river
Author creator: C.J. Cherryh
==== Stilcho ====
Ethnicity: a Sanctuary native. One source calls him half Rankan, half Swamper ie from the Swamp of Night Secrets
Profession: Soldier/guardsman, onetime Stepson
Home: Sanctuary, alive or dead
Author creator: C.J. Cherryh
==== Critias ====
Ethnicity: Syrese
Profession: Mercenary (Stepson)
Home: ...
Author creator: Janet Morris
==== Roxane "Death's Queen" ====
Ethnicity: Nisibisi
Profession: Witch/necromancer
Home: by the river
Author/Creator: Janet Morris