- Not to be confused with the actual location from Superman
Starring the Voices of
- Anais Fairweather as Supergirl
- Grey Griffin as Wonder Woman
- Erica Lindbeck as Mera
- Danica McKellar as Frost
- Matthew Mercer as Captain Cold
- Mae Whitman as Batgirl
- Yvette Nicole Brown as Bumblebee's Mom / Principal Waller
- Kevin Michael Richardson as Trigon
- Cristina Milizia as Jessica Cruz
- Tara Strong as Harley Quinn / Poison Ivy / Raven
- Originally scheduled to be released in the fourth season, despite a couple clips appearing in the sizzle reel for that season, this webisode was moved to Season 5 to coincide with Mera's appearance in Aquaman at the time the film was first set for a July 27 theatrical release, later October 5 until it was delayed again to December 21. In addition, this webisode marks the last to be written by Shea Fontana.
- The title references Supergirl's location. But unlike its comic book counterpart that's placed inside of a icositetrahedro, the DC Super Hero Girls version of the Fortress of Solidarity bears a resemblance to the famous Superman location Fortress of Solitude, only at the North Pole instead of the South.
- This webisode marks the third Season 5 webisode to air both parts together. Had it aired in the previous season, it would've been released as the two-part season finale.