List of Probable Candidates:
1. Trixie (Being Starlight's first new friend in many years, Trixie will undoubtedly play a main role in the story.) Confirmed
2. Gilda (She would definitely want to help save Rainbow Dash.)
3. Gabby (She has Pinkie Pie's energetic and extrovert personality.)
4. Sunburst (Starlight and Sunburst's friendship might be a crucial factor in dealing with the unknown threat.)
5. Thorax (He would want to repay the debt to Spike and Twilight for helping him be accepted into the Crystal Empire.) Confirmed
6. Cutie Mark Crusaders (They wouldn't want to sit around doing nothing while their big sisters are being held hostage.)
7. Maud Pie (She cares very much for her little sister, Pinkie Pie, and wouldn't like knowing that she was in danger.)
8. Shining Armor (For helping him so many times in the past, it's time for Shining Armor to help Twilight Sparkle in return.) Jossed as he is revealed to be kidnapped along with his family.
9. Big Mac (Like a true Apple family pony, Big Mac will step up to the challenge to help save his sister, Applejack.)
10. Lightning Dust (Starlight could easily understand that she would want a chance to redeem herself and become friends with Rainbow Dash again.)
11. Moondancer (As one of Twilight's first fillyhood friends, Moondancer might be willing to help save her.)
12. Princess Ember (If Spike is captured as well and the threat to Equestria extends to the Dragonlands, then Princess Ember will have to help Starlight to protect both ponies and dragons.)
13. Double Diamond, Sugar Belle, Party Favor, Night Glider (They helped the Mane Six get their cutie marks back and forgave Starlight for her misguided ways.)
14. Zephyr Breeze (Fluttershy helped him into finding the courage to try and succeed in Mane Therapy School and is the most unlikely character to be considered a hero.)
- The team consisted of Starlight, Thorax, Trixie, and Discord.
- Considering the episode title appears to represent cyclical natures, it could be Celestia's evil form, Nightmare Star.
- Or we could have Grogar finally appear.
- Since the summary says a past villain is returning, it's probably Queen Chrysalis.
- It could just as easily be King Sombra. If so, it wouldn't be the first time that an issue of My Little Pony: FIENDship Is Magic became Retcanoned.
- The Sirens (so powerful that Starswirl was only able to defeat them by sending them to a dimension without magic) could have found their way back to Equestria from the My Little Pony: Equestria Girls universe through the portal, which is now permanently open. Nice Job Breaking It, Twilight.
- It could even be the legendary wizard Starswirl the Bearded himself. There has to be some reason why he isn't widely known outside the Canterlot intelligentsia; perhaps there's an untold tale of him Jumping Off the Slippery Slope.
- It could be a completely new villain who happens to be the first one ponykind ever encountered in-universe.
- The villain of the two parter is confirmed to be Queen Chrysalis, and the Changelings.
- Completely Jossed; the Everfree Forest is not visited, only one of Starlight's friends is present, and the group is only four members strong.
- Confirmed: The Changeling Kingdom.