|“||He told me he wouldn't hurt...Charlie. He lied to me.||”|
–Silena, with her dying breath, in The Last Olympian
As revealed in The Last Olympian, at some point shortly before he left Camp Half-Blood, Luke confronts Silena, charms her, and persuades her to become his spy by telling her that she would be saving lives. Afterwards, she wanted to stop being a spy for the Titans, but Luke blackmailed her saying that he would reveal her secret if she ever stopped and would harm Charles Beckendorf, her crush.
Silena is shown to be in charge of the Pegasus stable. She gives Percy his first riding lesson on a pegasus. Percy Jackson thinks she is very pretty and describes her as, "one of the nicer Aphrodite girls."
It can be assumed that Silena was how Luke already knew about Tyson before meeting him.
When the Hunters of Artemis visit Camp Half-Blood, Silena is not happy briefly having a sparring match with them and leading to her participation in Capture the Flag. Zoë Nightshade taunts her about her mother and about her strong belief in love. She mocks Silena about her desire to not be seen, though she is the daughter of the love goddess. Silena is shown to be passionate and furious towards those who deny the existence of love (especially the Hunters of Artemis), as shown when she grumbled, "I'll show them 'Love is worthless'. I'll pulverize them!"
Silena makes a brief appearance when Percy first arrives in the camp riding a pegasus. Later, she is checking off the cabins, making sure they are clean and in order, and awarding points and prizes for the cleanest cabin. She smiles (with a wink) at Percy when his cabin is spotless and has beautiful adornments (thanks to Tyson who was right there in the cabin when Percy entered). It is noted that she is very brutal about ratings of cabins with bare walls. If she sees one little speck of dirt, Silena starts giving criticisms. She likes things nice and pretty.Annabeth Chase's team are up against Percy's and Charles Beckendorf's team. Silena and Annabeth capture Percy, but he tells them that Beckendorf is captured by the Myrmekes. Banding together, Silena and Annabeth bravely help Percy find the Bronze Dragon and put it back together, saving Beckendorf. Afterwards, Beckendorf asks Silena to the fireworks, which is the most romantic event that Camp Half-Blood has every year. It is possible that the events in the story were a plan by Silena with Annabeth's help to get Beckendorf to build up enough confidence to ask Silena out, but the smiling girls do not confirm it when Percy confronts them about it. It also said that Silena had tried to give Annabeth a makeover.
Silena takes part in the Battle of Manhattan with the other demigods, but is devastated after Beckendorf's death. During the battle, she goes up to Olympus and hears Percy's orders. She passed the information to Kronos that the Ares cabin wasn't there to defeat the Lydian Drakon. She goes back to Camp Half-Blood to convince the Ares Cabin to fight while the battle's raging on in New York as she and Clarisse are best friends. It is said that Silena tries to convince Clarisse to come, but she refuses. Later she leads the Ares cabin into battle dressed in Clarisse's armor and fights against the Lydian Drakon, even though a child of Ares is destined to kill it. Percy noticed that her voice was strangely shrilly, but didn't think anything about it at the time, given the monster she was facing. Right before she charged the drakon, Percy saw that she had blue eyes, realizing too late that she wan't Clarisse. She then gets hit with drakon poison in the face and while dying she reveals that she was Kronos' spy. She did it because before she liked Charles Beckendorf, she was charmed by Luke Castellan, who convinced her that she would be saving lives and that Charlie wouldn't be hurt.
Afterwards, she wanted to stop being a spy, but Luke blackmailed her saying that he would reveal her secret if she ever stopped. Her last words were "Charlie... See Charlie...". She eventually joins Beckendorf in Elysium, revealing that Silena was the person Beckendorf was waiting for in the start of The Last Olympian. This mirrors an event in the Trojan War when Achilles' cousin, Patroclus, leads their army into battle because Achilles refuses to go. Patroclus is killed by Hector and after that Achilles brutally kills Hector, like how Clarisse goes on a rampage after Silena's death. Because the campers held Silena in high regard, no one says the word "spy" during the burning of her shroud, which is described as hot pink with an electric spear embroidered on it. The campers of Ares' cabin and Aphrodite's cabin and the entire camp itself claim that she is a hero except Drew.
Although deceased, Silena is mentioned by Annabeth while she gives Piper McLean a tour of Camp Half-Blood, who says that Silena was great person. When Piper asks what happened to Silena, Annabeth stays silent for a moment but doesn't answer and instead tells Piper that they should continue the tour. Silena is later mentioned by Drew, her replacement and the new head counselor of the Aphrodite cabin, during Piper's first night in the Aphrodite cabin after she is claimed. According to Drew, Silena didn't complete Aphrodite's Rite of Passage, and deserved what she got. The situation continues to spin out of control as Drew denounces her as a traitor, angering the other cabin members. In confidence however, Piper, the Ares cabin, all members of Aphrodite's Cabin (bar Drew), and those that knew her when she was still alive firmly believed that she was a hero. Drew cited two main points of contention in regards to Silena's choice of actions; Silena's former alliance with Kronos and because Silena fell in love and stayed in love. Despite never meeting her, Piper respects her greatly (possibly) due to her relationship with Jason mirroring that of Silena's and Beckendorf's; both children of Aphrodite fell in love and refused to break the heart of the person they love.
While at the River Acheron, Percy and Annabeth are plagued with thoughts about how they were not so different from the damned souls, considering the deaths they "could have prevented." Silena was mentioned as one of these. Annabeth was forced to remember how she and Michael Yew had died in the Battle of Manhattan.
She is noted to be kind and caring to the other campers. Percy once described her as one of the nicest girls in the Aphrodite cabin (far less shallow and conceited than most of her cabin mates), also saying that Silena was a neat freak. She loved Beckendorf, and began to date him after The Demigod Files, but before Beckendorf, she liked Luke and became his spy. Later on, she stopped liking Luke, leading him to blackmail her into giving him information by saying he would not harm Beckendorf as an agreement. Being a daughter of Aphrodite, she cares strongly for the people she loves. After the death of Beckendorf in The Last Olympian, she becomes filled with guilt, but it doesn't stop her from helping her fellow campers and coming clean before she dies.
In The Titan's Curse, she tells people not to look at her, and Zoe Nightshade replies saying, "A daughter of Aphrodite who doesn't wish to be looked at?" Silena tries to slap Zoe, but is restrained by Connor and Travis. This shows that she can speak out and stick up for herself, and does not stand by just looking pretty, unlike many of her other cabin mates.
It is unknown what Silena definitely looks like, as her appearance tends to change between books. In The Demigod Files, it said that her hair was black and her eyes chocolate brown. In The Last Olympian, she had brown hair and blue eyes and in The Ultimate Guide, her eyes were blue and her hair was blonde. In all descriptions, she is described slim. It is always stated that she is a very beautiful girl who everyone stares at. Since she is a daughter of Aphrodite, she may have the ability to alter her physical appearances or she simply gets bored of her appearance (likely due to her ADHD) and changes them. However, according to Rick Riordan in an interview, she officially has black hair and blue eyes.
- Amokinesis: As the daughter of Aphrodite, she has absolute control over love and desire.
- Appearance Alteration: She had the ability to change her physical features as Aphrodite is the goddess of beauty, as she had blonde hair and blue eyes in The Ultimate Guide, but had black hair and chocolate brown eyes in The Demigod Files and brown hair and blue eyes in The Last Olympian.
- Beauty Manipulation: She had magical control over clothes, makeup, and jewelry.
- Love Magic: She knew a minor degree of love magic.
- Expert Rider: She was an expert Pegasus rider, and was the one to teach the skill to Percy.
- French: She was fluent in French, due to it being the "language of love."
In The Bronze Dragon, it was stated that Charles Beckendorf had a not-so-secret crush on Silena for three years. At the end of the book, he asked Silena to the fireworks, to which she replied that she though he would never ask. Silena is the only person who calls him "Charlie". Silena blames herself for Beckendorf's death, as she was Luke's spy at camp. In the end, Silena joins Beckendorf in Elysium.
It was shown in The Last Olympian that Clarisse was devastated by Silena's death, as the two were good friends at camp. Silena's death sent Clarisse into a rage and, she single-handedly slayed the drakon that had killed Silena without armor. Clarisse always spoke of Silena as a hero after her death, despite the fact that she betrayed Olympus.
Silena, a variation of Selena, is of Greek origin and means "moon." Beau regard is French for "beautiful look."
- Her relationship with Charles Beckendorf may be a reference to the marriage of Hephaestus and Aphrodite. Her friendship with Clarisse may also be a reference to the not-so-secret infidelity of Ares and Aphrodite, although it is not romantic. They also shared the same half-siblings, Phobos and Deimos.
- In battle, she wears pink and red armor which Percy says makes her look like a "Guerrilla Warfare Barbie."
- In The Titan's Curse, Silena is present at the leaders meeting meaning she must stay at Camp all year round.
- Silena is the only known character to call Charles Beckendorf "Charlie", while others call him Beckendorf.
- Silena and Clarisse mirror Patroclus and Achilles. Achilles refused to fight, so his cousin Patroclus lead the Greeks in Achilles' armor. Hector of Troy killed Patroclus and in rage for what happened to him, Achilles joined the fight and dragged Hector's lifeless body around in his chariot. Silena disguised herself as Clarisse, was killed and only then did Clarisse rejoin the fight, defeating and dragging the drakon around.
- She may be related to General Beauregard, a famous soldier at the start of the American Civil War. Aphrodite mentions that he was a womanizer, as he was married to his second wife when Fort Sumter was shelled, although he had eyes for Lisbeth Cooper.
- Silena had blonde hair and blue eyes in The Ultimate Guide, but had black hair and chocolate brown eyes in The Demigod Files and brown hair and blue eyes in The Last Olympian.
- This could be because of her shapeshifting powers, inherited from her mother, Aphrodite.