Deliora Returns is an event that takes place during the Galuna Island arc.
Having been informed of the curse of Galuna Island and the need to destroy the moon, Natsu, Gray, Lucy and Happy take rest in a village house and discuss their situation. Despite Natsu and Happy's enthusiasm, they soon come to the obvious conclusion that destroying the moon is not possible and they must find another way to save the villagers. Deciding to explore the island tomorrow, the Mages take rest for the night, to Lucy's dismay as she sleeps between Natsu and Gray.
The next morning, the team leaves the village and heads into the forest to investigate. While discussing how destroying the moon would result in adverse effects, the Mages encounter a giant rat which quickly attacks them with its foul breath. The strong stench quickly takes down Natsu due to his sensitive smell as well as keeping Gray down while Lucy remains safe inside Horologium. The Mages quickly make a run for it as Gray soon uses Ice-Make floor, causing the giant rat to slip, knocking it out. As Natsu and Gray continue hitting the mouse, Lucy points out a nearby structure.
As the Mages explore the building, Gray and Natsu discuss some markings on the wall while Lucy ponders their meaning. Thinking about the shape of the floor, Natsu stomps on it and causes it to break, resulting in the Mages falling below with Happy unable to bring them back up.
Upon landing, the group finds themselves in a secret cavern underneath the ruins and decides to start exploring. As they travel, Natsu runs down a path and finds something which immediately draws his attention. Soon, Lucy, Happy and Gray see what Natsu found, with the latter incredibly shocked. Inside a large block of ice, a frozen Demon exists, which Gray calls Deliora. As he looks upon the creature, Gray angrily expresses frustration over its presence, stating it shouldn't be here. As he mentions it as the "demon of disaster", Natsu hears someone approaching, causing the group to hide.
Two men, a short one with thick-eyebrows and tall one with dog-like ears soon arrive, wondering about the voices that supposedly came from the area. The short one teases the tall one, asking if his ears are a result of the Moon Drip, to which he angrily responds that they're just decorative. While the two talk, a girl with pink hair arrives, claiming that someone hurt Angelica, noting them to be intruders. The three decide that for having seen Deliora, the intruders must be eliminated and leave to meet their master Reitei.
After the mysterious Mages leave, Gray explains that the Demon they see in the ice once wreaked havoc in his hometown and was sealed by his teacher Ur, surprising the others. Clenching his fists, Gray angrily claims he won't let "Reitei" carry out his plan. As Natsu readies to defeat the Demon with his Magic before it can be revived, Gray punches him, telling him he can't release it or it will be unstoppable, though Natsu questions if it can be released so easily.
Gray explains that the ice Deliora is sealed in is an unmeltable ice and begins wondering why it was brought to the island if it couldn't be melted. When Lucy suggests that melting the ice was itself the purpose of the transfer, Gray questions the reason for it. Natsu suggests they question the people they saw but Gray states they should instead wait for night as the moon would be up by that time.
As Gray recalls memories of his teacher Ur, Lucy summons her Celestial Spirit Lyra to sing a song as they pass the time. As Lyra begins playing, Happy, Lucy and Natsu enter states of relaxation while Gray begins crying. Lucy and Happy notice this, with the former commenting that Lyra can reflect people's hearts through her songs. Soon after, the moon arises and begins shining on Deliora, resulting in the Fairy Tail Mages exiting the ruins to investigate the issue.