|Full name:||Dexter O'Neil|
|Alias:||Dexter Brannick (by Aislinn Brannick)|
|Nicknames:||Dex (by Romy Hayden, Izzy Brannick)|
|Family:||Unnamed (grandmother) †|
|Friends:|| Izzy Brannick|
|First appearance:||School Spirits|
|Last appearance:||School Spirits|
Dex O'Neil is Izzy's friend. He was introduced in School Spirits.
Izzy Brannick first meets Dex when she is sent to run laps on the football field in gym class after dislocating Ben McCrary's shoulder. When Izzy shakes Dex's hand, she feels a shock that she believes is magic. Convinced that Dex is some kind of Prodigium, Izzy adds that to her list of things to do in Ideal, along with working with the Paranormal Management Society (PMS) to hunt and stop the ghost of Mary Evans from hurting/killing the descendants of the men that are later found to have set her on fire. Dex's best friends, Anderson and Romy, sit with him at the basketball game where Izzy attends with Adam Lipinsky. On a trip to the cave, the place of Mary's death, Izzy and Dex kiss, but while Izzy is convinced that they are both under a love spell, Dex isn't so sure. Dex takes Izzy to meet his grandmother, and Izzy is amazed by Nana's delicious cooking. Shortly after Izzy leaves PMS, Dex quits 'very dramatically'. The two of them go back to the cave, kiss, and then work together with the help of Maya to rid Mary's ghost for good, until Nana walks in and tells them that there is only one way to save Romy, who Mary had possessed, and get rid of the ghost. Nana then cuts an 'x' in her palm, and lays it on Romy, sacrificing herself to keep Dex alive. Dex is shaken by the whole experience and returns to the Brannick house with Izzy and Maya, meeting Torin and Aislinn Brannick. Izzy's mom, Aislinn, reluctantly agrees to take him in, and Dex joins the Brannick family under the name "Dexter Brannick".