Team Natsu & Gajeel Redfox vs. Celestial Spirit King (Eclipse)

Team Natsu & Gajeel Redfox vs. Celestial Spirit King (Eclipse) is an anime-exclusive fight fought between Fairy Tail Mages Natsu Dragneel, Happy, Lucy Heartfilia, Erza Scarlet, Gray Fullbuster, Gajeel Redfox and Eclipse Celestial Spirit King.

Prologue
After reaching the Celestial Spirit World, the Mages are shock to see what seems to be the eclipsed Celestial Spirit King. After the latter absorbed the 12 Zodiac Spirits, the Mages decide to attack him. Gray and Juvia deliver the first attack, which turn effectless. The guild then attacks the king consequently, yet again with no effect. The Eclipsed King keeps overwhelming the Mages and then starts turning his opponents into star constellations, until only Natsu, Happy, Lucy, Gray, Erza and Gajeel are left.

Battle
With Natsu's attacks are effectless on the king, the Mages keep attacking but in vain, There are then outpowered by the Eclipse King unique physiology. The king then fires dark green beams from his body, similar to the one that striked Natsu before, overwhelming the Mages. Befitting their determined characters, the Mages rise yet again to continue their fight. After realizing that the twelve spirits are still alive, Natsu and Happy fly towards the Celestial Spirit Beast to rescue them and enters the beast's mouth, leaving the outside for his comrades.

The Celestial Spirit Beast then starts shapeshifting into a more distinctive form and continue attacking the Mages, while Natsu and Happy wander in his stomach, reaching a vast space. Natsu then finds himself targeted by the king's immune system, in which he defeats one by one, while the rest of the team manage to bring damage on the Eclipsed Beast. Natsu and Happy eventually find the core of the beast with the Celestial Spirit King chained into it. As it starts dragging him into the core, Natsu tries attacking the chains but in vain. The thirteen chains are revealed to be the zodiac spirits, leading Natsu to decide to wake the king up. Meantime, after the eclipse king, changed forms again, the team keeps attacking with it's full power, believing that Natsu will save their friends. The Dragon Slayer starts eating the core's matter. With the new power he gained, Natsu then casts Planetary Flames: Exploding Flame Blade, destroying the spirit's core, blowing up the Eclipse Celestial Spirit King into pieces.

Aftermath
After the battle, Erza pulls Natsu and Happy from the rubble, alongside the Celestial Spirit King. The Celestial Spirit World then returns to normal, as well as the rest of the spirits and the king, with no one of them remembering anything from what had happened. .