Chapters: N/A, Episodes: 128-150
Short SummaryA filler arc that takes place after the Seven Years Arc. A mysterious girl name Michelle suddenly comes looking for Lucy, delivering a clock key as her inheritance from her father. However a militia like church is likewise after the key and the clock pieces of which it unlocks. Forcing the Fairy Tail members to search for the pieces before they do and try to stop their plan.
Key of the Starry Sky Arc has the following tropes:
- Arc Villain/Big Bad: Ultimately Midnight or "Brain II" as he now calls himself.
- Back from the Dead: Klodoa, who was crushed by Zero in the Oracion Seis Arc.
- Bittersweet Ending: Oracion Seis is stopped and the Infinity Clock is destroyed. But Michelle/Imitatia is reverted back into a doll. Cobra has to leave Kinana again after briefly reuniting with her. And the Legion Corp, while making peace and apologizing to Fairy Tail for their actions, have to set out and find the clock pieces once more which will likely take their lifetimes to locate. The beginning of the Grand Magic Games arc also reveals that Fairy Tail's actions in this arc have likewise not won them over with the public.
- Blob Monster: Sugarboy's power which summons blob monster that sap one's strength.
- Broken Aesop: Erza spends a lot of time trying to shove down Cobra's throat that The Power of Friendship is better than power gained through sacrifice... and then beats him only because he got distracted when he heard his friend Cubelios/Kinana coming. To be fair, he did have her on the ropes and was on the verge of beating her when it happened. Plus Erza and the rest of the protagonists were on a time limit at that point to save Lucy and needing to defeat him to break the seal on the Infinity Clock.
- Church of Happyology: The Zentopia Church
- Continuity Nod: Midnight uses the same spell on Natsu that Zero did back in the Oracian Seis Arc which would've been the end for him as Natsu didn't have the Flame of Rebuke to burn out of it that time. However thanks to Lucy using the power of the Infinity Clock and turning it against Midnight, Natsu is able to break free.
- Gotta Collect Them All: The clock parts.
- Designated Girl Fight: Mirajane VS Mary Hughes. But this trope is averted for the rest of the arc.
- Disney Villain Death: Midnight is defeated by being knocked into a rock wall by Natsu which crumbles and sends him falling into an abyss. Subverted though as Midnight survives and reappears in the story later with the rest of the Oracion Seis in the Tartaros Arc.
- Distaff Counterpart: Mary Hughes to her Edolas counterpart, and Dan who fills in for Erza Knightwalker.
- Fusion Dance: Mary does this in the climax of her fight against the Strauss siblings by stealing and later merging with Mirajane's Satan Soul form.
- Heel–Face Turn:
- Earthland Coco. In fact, it pretty similar to her Edolas counterpart as she both befriends Lucy and switch sides after questioning her group's motives.
- Likewise Imitatia near the end of the arc after realizing the Infinity Clock was erase Lucy's existence when it absorbs her.
- Hoist by His Own Petard: Midnight aka Brain II is beaten when he realizes at the last moment that the Oración Seis's seals were likewise preventing Lucy from taking over the clock. With the rest of the members beaten (including Imitaia by his own hand no less) Lucy was able to take control of the Infinity Clock and turn it against him while saving Natsu from Midnight's ultimate attack. Which allowed Natsu to beat him in a more even fight.
- Mêlée à Trois: Between Fairy Tail, the Legion Corps, and later Oración Seis.
- My Master, Right or Wrong: The Legion Crops go through this in the second half of the arc when the Zenotopia's Arch-Bishop gives them orders to attack fellow churches for no particular reason. It's later found out the Zenotopia church second in command, Lapointe, was a puppet controlled by the Oración Seis's who was brainwashing the Arch-Bishop for their plans and in turn, using the Legion members as pawns.
- Nice Job Breaking It, Hero!: Fairy Tail manage to collect all the clock parts. But in doing so they gather them all in one place for the Oración Seis to take from them later and activate the doomsday device. They also find out later that they were just supposed to protect the clock part Lucy's father sent, not collect the pieces.
- Oh, Crap!:
- Mary Hughes when Mirajane switches to her Satan Soul: Halphas form and trashes her completely despite having taken control of Mirajane's first Satan Soul form.
- Lucy when she re-read the Starry Sky book and realizes she was just suppose to protect the clock piece given to her not collect the parts.
- Gildarts and Laki when they find a comatose woman in one of the Zenotopia churches and find out her name is Michelle Lobster, coming to the realization the "Michelle" traveling with Lucy is fake.
- Imitatia when Midnight reveals the Infinity Clock will absorb Lucy and cause everyone, her included, to forget her existence which is the opposite of what Imitatia wanted.
- Midnight when he realizes that the Oración Seis's seals were the only things keeping Lucy in check as she's merged with the Infinity Clock. With all the members now beaten, the seal is too weak and she can use the clock's power against him.
- People Puppets: Mary Hughes power, which, unlike her Edolas counterpart, can actually control people.
- Poor Communication Kills:
- If the Zentopia church had bothered to tell Fairy Tail what the clock pieces were for in the first place rather then attacking them, none of this would've happened.
- Likewise the case with Michelle/Imitatia who could've prevented the whole arc from happening if she had just simply told Lucy who she really was when they first met instead of blindly following Brain II.
- Unexpected Inheritance: The clock hand Lucy's father leaves to her.
- Walking the Earth: The ultimate fate of the Legion Corps after everything concludes. They once more go to search for the clock pieces but as the pieces no longer have magical power, it'll be more difficult to find them and likely will take them their lifetime to locate all of them.
- Wham Episode: Gildarts and Laki manage to infiltrate one of the Zentopia's churches and defeat the inhuman church members inside. However, as they go further inside they find a woman in a comatose state being kept alive by a magical machine. Reading her charts they find that she's Michelle Lobster. The following episode reveals that the Michelle who was traveling with Lucy's group is indeed a spy, the true sixth member of the Oración Seis, who calls herself Imitatia later revealed to be a doll of Lucy's that Midnight brought to life.