In Keziah's Song, "the Seleucids" take centre stage as the story's first villains. They are referred to by characters in the novel as "Seleucids," and sometimes as "the Greeks." So who were these people? Were they just the Greek Empire, but going by another name? Well, almost. But not quite.
The Greeks are an ancient people, and I don't just mean ancient from our 21st-century vantage point. When Keziah's Song starts in 135 BCE, the Greek civilization was already over a thousand years old. However, Greek history isn't famous in modern western society until Leonidas and his three hundred Spartans show up in the history books. Leonidas and his men are renowned for their battle against Xerxes and the Persian army at Thermopylae in 480 BCE.
Not too long after Leonidas, Socrates became the next best-known Greek. Socrates was not famous for war, but rather philosophy. After Socrates came his student, Plato. By the mid-to-late 300s BCE, we find both of these types of Greek characters in the spotlight: Aristotle (for Philosophy) and Alexander the Great (for War), and it is with Alexander the Great that we get the Greek Empire.
The Greek Empire, as a world power, did not last long in a unified form. After Alexander's death, the empire broke up into four parts. Though each part governed itself independently (and sometimes fought wars against each other), they maintained the same language as well as the cultural identity that eventually became known as Hellenism.
The Egyptian part of that fractured empire was ruled first by a guy named Ptolemy, and so Egypt became known for a while as the Ptolemaic Empire. The Pharaohs who ruled the Ptolemaic Empire were really Greeks, and these Greeks kept things very much in the family: brothers married sisters, nieces married their uncles and so on. They also liked to stick to a small handful of names, so we wind up with fifteen Ptolemys, seven Cleopatras and at least three Berenices. We now put numbers after their names to keep them straight, but that wasn't a thing in Keziah's day. The Egyptian Cleopatra early in Keziah's Song we now call Cleopatra III and the one who deals with her son Lathyrus, at the end of the book, we call Cleopatra IV. The most famous Cleopatra—the one we associate with Mark Anthony—is Cleopatra VII. She's not in Keziah's Song. She's coming, but not for a few books yet.
Okay, so that's the Egyptian part of the old Greek Empire. Two other parts of the old Greek Empire can be dispensed with fairly quickly: the Macedonian Empire (basically what we think of today as Greece proper) and the Attalid Empire (roughly western Turkey today). Rome conquered the Macedonian Empire a decade before Keziah's Song starts and then absorbed the Attalid Empire about a year after Keziah found the lute at Grandma Sara's house.
So, for the bulk of Keziah's Song, there were only two parts of the original Greek Empire remaining: the Ptolemies in Egypt, and the Seleucids, who maintained control of what today we call eastern Turkey, Syria, Lebanon, parts of Iran and so on. The Seleucid Greeks were not as incestuous as the Ptolemies, but they did prefer a limited catalogue of names like their Ptolemaic cousins. There were seven guys named Seleucus, thirteen named Antiochus, four women called Berenice (also a popular name with the Egyptian Greeks you'll recall), three named Demetrius, multiple Cleopatras (not to be confused with the Egyptian Cleopatras) and so on. Remember that numbering these people was not a thing back then and as a result, trying to write a fast-moving novel in this context, with everybody going by the same few names, was enough to drive this novelist a little crazy in the early drafts. When the niece of someone turns out to also be the wife of that very same person, well, let me say there was some severe hair pulling going on while I tried to manage the confusion in those first early drafts.
Thank heavens that the Jewish people were a little more creative with their kid's names and will stay that way until Book Three. By Book Three, the Jews start acting more like Greek-Hellenists, and a minor part of that culture shift is the minimizing of name options for their kids as well. But that's a problem for Book Three. For Keziah's Song, the Jewish names are easy to keep straight.
So, back to the original question: what is a Seleucid? A Seleucid is a citizen of the nation that was one-fourth of Alexander the Great's original empire. By the time of Keziah's Song, it was only one of two surviving parts of that originally four-part empire. At the beginning of the novel, two of their brother-kingdoms have fallen to Rome, but the Seleucid Empire (Turkey, Syria, Lebanon, Iran) and the Ptolemaic Empire (Egypt) are still going strong. And the Seleucids are the villains. At least at the beginning of the novel, they are the villains. I think you'll agree that Jerusalem takes over the villain's role by the end of the story, but that might be giving too much away.
One last thought: none of my early readers identified Jugurtha as a villain. In fact, for my beta readers, he was one of the most popular characters. What did you think of Jugurtha?