A teenager named Luke Masters is chosen by an old hermit to hunt down beings called Dark Spirits who disguise themselves as normal humans, some of them being closer than they expect.
- Luke Masters (voiced by Scott Menville) - an athletic teenager who learns about the Dark Spirits' existence and starts to hunt down them while he handles with high school life as well.
- Scott Field (voiced by Bumper Robinson) - Luke's comedic best friend who is fascinated with popularity and helps Luke with hunting Dark Spirits, even if he mainly does it to be famous.
- Lola Robinson (voiced by Mae Whitman) - a studious Dark Spirit teenager who originally joins Luke and Scott as a spy, eventually fully redeeming and developing a crush on Luke on Season 3.
- The Mystic Dude (voiced by Corey Burton) - a wise shaman who guides the trio by providing them useful information about anything they need, including the weaknesses of Dark Spirits.
- Mr. and Mrs. Masters (voiced by Daran Norris and Grey Griffin, respectively) - Luke's protective parents who are usually out to TBD.
- Khalid Snow (voiced by Khary Payton) - a stereotypical black teenager who often makes some jokes about TBD.
- Jordan Richardson (voiced by Benjamin Diskin) - a cocky teenager who shows TBD.
- Evelyn Rhodes (voiced by Jessica DiCicco) - a flirtatious teenager who likes to tease other boys, especially Luke, and often sees Lola as a rival to TBD.
- Cristina Rodriguez (voiced by Alanna Ubach) - a fashionista teenager who usually does makeup and TBD tutorials online while also enjoying to TBD.
- Mr. Jacobson (voiced by Jeff Bennett) - a wild yet protective Math teacher who is aware of the existence of Dark Humans and warns Luke about them.
- Mrs. Jacobson (voiced by Tara Strong) - a friendly Science teacher and Mr. Jacobson's wife who is an expert on the idea of supernatural, occasionally giving some advice to Luke and his friends.
- Leonardo Knight (voiced by Matthew Mercer) - a rich and sinister businessman who is guarding a strange amulet that allows him to summon Dark Spirits, being their ruler.
- Martha (voiced by Catherine Taber) - Leonardo's [ideas] secretary who TBD.
- Markus (voiced by Peter MacNicol) - an insane human who worships the Dark Spirits and aims to become one of them himself, often seeking for the complete control TBD.
- Nevora (voiced by Olivia d'Abo) - the cold first Dark Spirit who plots to use Lola as a host to open TBD.
- [season 4 villain, male, Dark Spirit] (voiced by TBD) - TBD
- [Light Spirit, name like that] (voiced by TBD) - TBD
- Katherine Stormweather (voiced by Danica McKellar) - the rude captain of the cheerleading team who is actually a Dark Spirit and is out to discover power for her own.
- Lara Johnson (voiced by Ashley Johnson) - a stupid cheerleader who, like her teammates, is a Dark Spirit and usually gets into situations.
- LaShawna Brooks (voiced by Kimberly Brooks) - a rather cynical but TBD cheerleader who Scott has a crush on, being also a Dark Spirit and aids them with their plans, even if she spends most of the time feuding with Katherine.
- Karen Kawashi (voiced by Janice Kawaye) - a boy-obsessed cheerleader who often TBD.
- Marvin the Mystic (voiced by Tom Kenny) - a flamboyant Dark Spirit magician who is able to create illusions to anyone he attacks by simply saying the words "Presto".
- Polka Dots the Clown (voiced by Hynden Walch) - a crazy Dark Spirit clown who loves to cause mayhem, often recurring to crazy shenanigans like smoke bombs or bear traps, apparently having a crush on Scott, much to his disgust and fear due to being terrified of clowns.
- Ella Zoode (voiced by Kath Soucie) - a cranky Dark Spirit zookeeper who can control animals and uses them to assemble an army of zoo animals to destroy the city.
- Old Man Bob (voiced by Armin Shimerman) - a TBD Dark Spirit old man who is rather crazy and is known for his constant paranoid nature.
- The Snappz, consisting of:
- Xander Reaction (voiced by Jason Spisak) - a TBD comic book artist who TBD.
- Darrell Slaye (voiced by Nolan North) - a TBD Dark Spirit killer who TBD.
- [Foolish character] (voiced by TBD) - a foolish Dark Spirit who TBD.
- [Mule] (voiced by TBD) - a dimwitted Dark Spirit mule creature who TBD.
- [Ghoul] (voiced by TBD) - a ghoul-like Dark Spirit who TBD.
The animation for the series is outsourced to AKOM Production, Ltd. in Seoul, South Korea.