Nikki doesn't technically appear, but in the epilogue Thalia announces that she is pregnant with her.
Nikki is born in the early hours of the morning. Her parents choose her name because it means "victory of the people" in Greek, and her birthday is the day after Kronos was defeated.
She and her older sister, Taylor, seem to share a close bond.
Nikki is a main character. She has nightmare about Kronos, along with Taylor.
It is established that Nikki is basically Taylor's best friend, along with Lisa.
In Echoes in the Night, Nikki is ten years old. She is 4'11 and weighs somewhere around 85 lbs. She has pale skin (but not ghostly pale, like her father and sister) with a spray of freckles. Her hair is light blonde, like Luke's, and she has Thalia's stormy-blue green eyes. Overall, she looks more like Thalia, just with blonde hair.
Nikki is a bit like Chibiusa Tsukino from Sailor Moon, but less bratty. She's usually brave, but she's afraid of the dark and can be a bit clingy and immature. Like all demigods, she has ADHD and dyslexia. She likes dark colors, like blue, red, and black, but she's not as gothic as Taylor and Thalia (if at all). She does like some gothic music, though. Nikki wants to be popular, often copying what she sees older girls doing to look cool. She's a little lazy at times and quite a slob, often leaving dirty dishes lying around for someone else to clean. She isn't quite sure if she feels like a teenager yet.
- Nikki can steal things without ever getting caught.
- Nikki can give people electric shocks, often burning their hair off or making them faint.
- Nikki has many other powers relating to stealing, the sky, etc.
- Nikki, being Luke and Thalia's child, is extraordinarily powerful.
- Thalia Grace-Castellan (Mother)
- Luke Castellan (Father)
- Taylor Grace-Castellan (Sister)
- Zeus (Maternal grandfather)
- Ms. Grace (Maternal grandmother, deceased)
- Hermes (Paternal grandfather)
- May Castellan (Paternal grandmother, most likely deceased)
- Travis Stoll, Connor Stoll (Half-uncles)
- She could have been Taylor's twin.
- Her name could have been Angelica.