The last character in Senta and the Steel Dragon is the second title character for the series-- the Steel Dragon himself. In fact, when the series was originally planned as a single book, the title was going to be "The Steel Dragon."
The Steel Dragon goes through more change than any other character in the entire series. In Book 0, he only appears as an egg afterall. :) In The Voyage of the Minotaur he is little more than a pet for the sorceress Zurfina, though she saves the term "Pet" for Senta. We don't even learn the dragon's name until the very last word of the book.
The Steel Dragon grows (a lot) and increases his intellect and various abilities a great deal from book to book. In the final book of the series, Book 5: The Two Dragons, he is as large as a railroad car, though still tiny compared to the other dragon in the story-- yes, he's one of the two dragons mentioned in the title.
I hoped the 25 regular readers of this blog have enjoyed a look at the characters in this book. In the next few days, I'll start my way through Book 2: The Dark and Forbidding Land.