Sydney has layered dark golden-blond hair that reaches just past her shoulders (although it grows longer and longer throughout the series) and brown eyes that turn gold in the light. According to Adrian, her eyes are molten gold when she stands in the light. Sydney is about 5'7" in height. She wears expensive makeup, applied to give her a natural look. As an Alchemist, her cheek adorns a golden lily tattoo infused with vampire magic however, in Silver Shadows it is seen to have bits of silver in it.
Sydney goes to Palm Springs in place of her sister, her intentions clear on protecting her sister from Keith, her father's 'golden boy' who raped her older sister, Carly Sage. She begins to develop feelings towards Adrian Ivashkov throughout the book, despite the Alchemist teachings that were drilled into her head. She, Eddie, and Jill all attend a posh private school named Amberwood Prep, where she meets Trey Juarez, an intelligent (though he tries hard to hide it) football playing human whom Sydney befriends right away. She also soon becomes friends with Kristi and Julia who take it upon themselves to teach Sydney high school social behaviour. Sydney helps Krisrti when she suffers from the side effect of the 'celestial' tattoo. Kristi is grearteful and helps Sydney stop the bullying that Jill receives by replacing Laurel's shampoo with something else she made, therefore calling a truce between the two parties . After finding Adrian in a miserable state, she helps him find financial aid for art classes at Carlton College, once again blurring the line between necessary Alchemist business and unnecessary personal actions.
Sydney and Adrian team up to find out the supplier of the illegal ingredients for the tattoo parlor Nevermore, and her findings redeem her image within the Alchemist society. It is also revealed that she has "foul" blood and has some kind of magic in her. Adrian becomes infatuated with her eyes and tells her that she is beautiful. Sydney becomes confused and is saved by the door opening, where Sonya Karp and Dimitri Belikov enter. They bring with them Angeline, one of the Keepers who will help keep an eye on Jill.
Sydney decides to look up self-defense spells and signs up for a self-defense class-Malachi Wolfe defense classes- with Adrian, which she thoroughly enjoys, though Adrian seems to have a hard time with it (later this is revealed to be because of Adrian's romantic feelings for her, it is hard for him to deal with all the close physical contact, meaning 'everything' to him, and 'nothing' to her). Later it is found out that the humans who attacked Sonya and Sydney are indeed vampire hunters, or, 'Warriors of the Light' as they call themselves. Sydney agrees to give Sonya a sample of her blood, and the results say that Moroi found bits of all four elements in her blood, though why that is, is still unknown. Sydney brushes it off as the result of the golden lily tattoo which employs moroi magic and compulsion The vampire hunters then kidnap Sonya, causing Sydney to leave her date with Brayden early. She reluctantly uses a magic spell to find Sonya, and finds out that Trey Juarez is, indeed, a vampire hunter. She makes a plan to save Sonya by talking the hunters out of it, when this fails, the guardians (as well as Angeline), with Alchemist's assistance, invade the hunters' compound and escape with Sonya, whilst Adrian found and got out with Sydney after she was forced to leave in a separate direction than Eddie and Sonya. Sydney later finds out that they were planning this invasion all along but no one told her, not even the Alchemists. This strengthens her suspicions of Alchemists and their principles. This causes the hunters to exile Trey and his family, but this causes no strain on Trey and Sydney's friendship.
Sydney and Adrian begin finding the young witches and Jackie's sister at a Old Victorian Motel where they met Alicia. At college party, Adrian makes Sydney a fiery heart t-shirt this leads to them passionately kissing on the floor of the college party, but only to find out that the witch that they were suppose to warn had been attacked and become comatose. Jackie's begins to take Sydney out to a national park where they practice fire spells. Marcus, with two more ex-Alchemists, meets up with Sydney. He tells her that they know for sure that Warriors of Light are involved with Alchemists but there is no hard proof. He tells her that if she can get that proof, video footage from the Alchemist archives, she can become one of them, and have the compelling lily tattoo broken. She agrees to this. With very helpful tips from Adrian, she is successfully seduces and lures Ian Jansen, an Alchemist with a huge crush on Sydney, in getting her in the headquarters where she steals video footage of one of the head Alchemists in talks with the head of the Warriors, confirming that the Alchemist had lied to her. Marcus then breaks her Golden Lily officially breaking her away from the Alchemists but to finally be free she needs too go to Mexcio to have another indigo tattoo inked over it
One day out with Adrian at the national park, Sydney makes a Callistana, a dragon which sees both Sydney and Adrian as its parents. Veronica begins visiting Sydney in her dreams, causing Adrian to create Spirit Dreams to protect Sydney from her. Once again they both visit the old hotel, where they find that Veronica had left very quickly. Sydney makes her mind up that she is going with Marcus and the others to Mexico, deeply hurting Adrian to the point where he got drunk. Several nights later, Jaclyn does not answer her mobile causing Sydney to panic, she gets Adrian to drive her to Jaclyn's house where they find that Alicia was the one that harmed Veronica and the other witches and wanted to comatose Jaclyn. Sydney fights Alicia and to the point where she defeats Alicia but she is happy that she didn't kill her. They both find Jaclyn in the grass just near her house.
Zoe confronts Sydney about all the time she is spending with her history teacher and running errands for her. Sydney defends herself telling that history is the only subject she had not studied already and how interesting it is. After some days she finally gets to meet an old formidable witch Inez. After talking to her, Sydney realizes that the indigo ink Marcus used to seal the golden lily tattoo is charmed with human magic and she can reproduce it with the right substrate. This research preoccupies her and results in decreasing the time she gets to spend with Zoe, which further breaches the bond between the sisters. Sydney tries to do 'damage control' by letting Zoe drive the new SUV whenever possible.
Then, Adrian and Sydney are called to the royal court to work on the strigoi vaccine. There she gets the required alchemist compounds to prepare another tattoo for Trey to test the success of the first. She also learns about dabbling and Adrian confesses that he had done it only once. She is angry with him. One night, Wesley and two other royals try to get Sydney to go with them so that they can drink her blood. Adrian appears to the rescue and hits Wesley in his head with treejitsu. The matter taken up by the guardians and the wrongdoers are punished, but Sydney, Adrian and Neil were sent off back to palm springs, right when Sydney had forgiven Adrian and they were about to get intimate. In the court, Neil was tattooed with Olive's (recently restored strigoi) blood as a defense against turning strigoi. While on the way back to palm springs, the car skids off the road and they are stuck on the road in the snow. So that they don't freeze from the cold, Sydney creates a fireball which is witnessed by Neil.
After being tattooed, Neil is eager to test it and convinces Sydney and Eddie to track a strigoi and lure him into turning him. A few days later, on her birthday, Sydney visits Adrian. Zoe also wanted to spend the day with her sister, so they had had a fight about it and Sydney finally convinced Zoe that they will spend the weekend together. After the gumbo dinner that Adrian put together with the help of his college friends Rowena and Cassie, they spend the rest of the night in the backseat of Sydney's Mazda (since the mustang is out of commission) with their clothes lying on the floor.
With the material she brought back from the court, Sydney prepares the alchemist compulsion tattoo ink(she had gotten the moroi blood charmed by Abe back at court). She also learns to use the tattooing needle. she tattoos Trey with it. It fails in compelling him and thus, her rock salt sealing ink was successful. Therefore, she starts producing the ink in large quantity for Marcus and his Merry Men.
When they first meet in Bloodlines, Trey doesn't trust her because of her Alchemist tattoo, which he assumes is a tattoo she got from Nevermore. However, he quickly warms up to her and they become friends. Sydney also changed her mind about attending a football game in order to give Trey some moral support, and Trey was only student who suspected that she was responsible for shutting Nevermore down. Trey, in return, gives Sydney free coffees and sets her up with Brayden, who is one of his co-workers. However, Trey also is secretly a member of the Warriors of Light, and participated in the attack on Sonya and Sydney. Sydney quickly realizes that she and Trey are both caught between obeying the groups they belong, and what their consciences are telling them. Trey sets up the meeting between Sydney and the other Warriors, showing that he trusts Sydney to keep her word. After he gets kicked out of the Warriors, he comments that he does not blame Sydney for what happened, and they continue to be friends. In The Fiery Heart, it is seen that Trey trusts Sydney to tattoo him with indigo ink that she created to prevent be mind controlled, but she also returned to the favor by keeping Angeline single. Trey saved Sydney's life in Los Angeles against the Strigoi. Sydney was happy that Trey had turned against the Warriors and started a romantic relationship with Angeline.
 38c6e68cf9