Seymour began as a stuffed leopard head at a garage sale. Dionysus saw it and was outraged that such a 'noble creature' would have its head stuffed and mounted on a wall. Being that the leopard is a sacred animal to Dionysus, he took it and granted it life, although he did not give Seymour a body. Chiron says that it was a better fate than his previous owner got.
The first time Jason Grace enters the Big House's main room, Seymour snarls at him, which surprises him greatly. Seymour is able to eat food, but when Jason discovers this, he wonders where the food goes. However, it is never found out, as Chiron tells him not to think too much about it.
At the end of the book, Seymour is specially brought into the meeting with all the senior counselors.
Ella is seen feeding him Cheetos.
After Apollo passes out, Dionysus places him in his brother’s bunk, scaring him once he awakened.
- Seymour is a leopard, which is a sacred animal to Dionysus, his creator.
- Seymour's favorite food are sausages.
- It is unknown where the food he eats goes.
- Revealed in The Lost Hero, page 63.