Leonid is a magician and guard of the Eighteenth Nome in St. Petersburg, Russia. He is first seen in The Throne of Fire as the guard in the Hermitage Museum. Later in the The Serpent's Shadow, he aids Carter and Sadie by telling them the plans of Kwai and Sarah Jacobi who are working for Apophis. He is following the path of Shu.
Leonid, unnamed, runs in on Carter and Sadie battling the Tjesu heru that came from Vlad the Inhaler's staff after Set saw Carter through his poorly made invisibility spell. He is holding a staff, showing that he is a magician. He runs off after seeing the monster and being convinced that the Kanes are not the bad guys.
After meeting the Kanes, Leonid realized that they aren't evil like Sarah Jacobi makes them out to be and interested in the Path of the Gods, begins secretly learning how to channel the power of Shu as he has always been a good air elementalist. Leonid succeeds in learning how to do so on his own, but after witnessing Jacobi and her lieutenant Kwai communicating with various monsters including Apophis himself, Leonid flees St. Petersburg, contacting Shu and convincing him to transport him to Sadie Kane in Brooklyn. Leonid is able to get the message across to Sadie despite not speaking much English that the rebels are going to attack the First Nome and she takes him to see Amos Kane. After hearing stories from Jacobi, Leonid fears that he will be possessed by Set and eat his face, however Sadie calms him. After the portal they use drops them high in the air, Leonid channels the power of Shu and flies them to near an entrance to the First Nome, surprising Sadie. Leonid is taken to Amos who uses a spell so they can all understand each other perfectly and Leonid explains what he's learned and where Jacobi's base is. Leonid participates in the battle in the Hall of Ages and is badly injured , but survives and is expected to make a full recovery.
He is last seen in the infirmary, recovering from his injuries, along with a few other magicians.
Leonid is described as a young man no more than seventeen wearing a grey military outfit with a wool coat and an over sized hat. He is also described as having enormous ears which Sadie believed were the only thing keeping his hat on his head.
Leonid is shown to be an intelligent, but nervous young man. When Sadie takes him to see Amos, he is nervous about meeting him after hearing that he'll supposedly eat his face and is nervous about Sadie's joking threat to turn him into a banana slug. However, he displays his intelligence and bravery by secretly studying the Path of the Gods which he knows is dangerous as if he is caught, Jacobi will have him killed. Leonid is able to learn how to channel the power of Shu all by himself with no training just by studying old scrolls and is able to summon Shu and convince him to transport him to Brooklyn despite Shu's apparent dislike of mortals. He was able to determine just by his brief meeting with the Kanes and the fact that they were so powerful but left him unharmed, that they weren't as evil as Jacobi claimed, being able to see past her lies even when so many other older and more experienced magicians couldn't. Leonid can't speak much English, but can get his point across and may be able to understand the language better than he can speak it as he seems to get what Sadie tries to tell him.
Leonid describes himself as a pretty good air elementalist even before he started studying the path of Shu, hence why he chose that particular god. He proves to be a skilled enough magician to learn the Path of the Gods with no assistance and no training within six months using just old scrolls. He is also able to summon a god (Shu) which is said to be difficult to do and has only been shown to be able to be done by powerful magicians. When he channels the powers of Shu, he is able to fly or at least levitate as shown when he holds onto Sadie and flies them from where the portal dropped them in mid-air to a spot near an entrance to the First Nome.
- Leonid is the first magician outside of the twenty-first nome to practice the path of the gods since ancient Egypt.