The Serial Killer of the Eternal Darkness

 is the thirty-first episode of the first season of Star Teens Unite!.

Summary
A scary and hideous-looking serial-killing monster called the Grue seeks revenge while raiding Arco Iris.

Debuts

 * Grue

Characters

 * Ella
 * Kevin/The White Knight
 * Inidra
 * Sandra
 * Felicia
 * Lisa
 * Tanya
 * Sheila
 * Bella
 * Ms. Diana Apple
 * Mr. George Thompson
 * Veronica
 * Grue

Voice Cast

 * Aimee Carrero - Tanya
 * Candi Milo - Ms. Diana Apple
 * Grey Griffin - Sandra
 * Jennifer Hale - Veronica
 * Josh Keaton - Kevin/The White Knight
 * Kari Wahlgren - Ella
 * Kate Micucci - Inidra
 * Kimberly Brooks - Sheila
 * Mark Hamill - Grue
 * Ron Perlman - Mr. George Thompson
 * Susanne Blakeslee - Bella, Townsperson
 * Tara Strong - Felicia
 * Vyvan Pham - Lisa

Trivia

 * Arco Iris's serial killer called the Grue makes his debut here.
 * In this episode onward, Danny Phantom fans will hear the Grue's voice to sound like that of Undergrowth.