Adaptational Badass: Haman. In contrast to his Biblical portrayal where he begs for his life after in the scene where Esther reveals his plan in front of the king, here he doesn't lose his cool and instead calmly casts doubt on her Jewish heritage, accusing her of trying to usurp a good position, then breaking speeches her as she fears the king may not believe her.
As the Good Book Says...: Rather than read from the boring history books like all the other wife candidates have had to do, Esther chooses to tell the king the story of Jacob, Rachel, and Leah, him becoming fascinated by it and her audacity to read something else when that could risk death.
The Federation: A great alliance of democratic Greeks and monotheistic Jews, unified in the belief that all humans are created equal. The whole thing sounding very much like Eagle Land. Of course, this alliance does not exist in the setting itself. However, it is often invoked as one of the main excuses to go genocidal on the Jews.
Final Solution: Both the Jews in the backstory and the enemy of the Jews in the story are openly and proudly genocidal.
Foregone Conclusion: Haman will be Hoist by His Own Petard, Mordecai will be promoted to his place, and a new decree will be made that basically defangs Haman's while still respecting the immutability of the Law of the Medes and the Persians.
Scary Black Man: Hegai is a subversion. The first time the girls see him is right after they've been abducted, so he's seen as frightening. Soon after, however, he's found to be a surprisingly erudite Gentle Giant who sympathizes with the girls and helps them adjust to their new life in the harem.
Would Be Rude to Say "Genocide": Of the kind where you call a genocide a glorious victory. To the point where the problem isn't the slaughter of women and children, but rather the failure to kill one pregnant woman.
You Should Know This Already: Certain plot points are skipped because the viewer is expected to already know them, such as the king learning Mordecai was never rewarded when his chronicles are read at night, or Esther inviting him and Haman to two dinners, instead cutting directly to the second dinner.