Hidden Treasures: the Sword and the Wind

Hidden Treasures: the Sword and the Wind is an event inside a dungeon's treasury where Asta and Yuno discover two powerful magical artefacts.

Prologue
After defeating Mars of the Diamond Kingdom and restraining him, the Clover Kingdom's mages proceed on entering the dungeon's treasury. Once inside, all of them immediately are in amazement after seeing the amount of treasures that are stored within it.

All of them quickly spread across the treasury as they begin to explore and discover various artifacts that they have never seen before. They are also tempted to try and use various magic items that are scattered among the golds and jewelries. They find items such as a casket that could transmit visuals over a distance, a jar of light, an orb that could levitate the user and a robe among others.

The young Magic Knights' actions quickly infuriates Klaus Lunette who believes that those items could be very precious and should not be handled carelessly.

Hidden Treasures: the Sword and the Wind
While exploring the treasury, Yuno notices that streams of wind are gathering around a scroll in which is place on top of a pedestal. He approaches the said scroll and opens it. Inside it, Yuno finds a series of writings that he could not comprehend. A moment later, his grimoire begins to release a bright alongside the scroll. When the light has faded, the writings have disappeared as Yuno does not understand everything that had just happened when Klaus asked him.

On the other side, Nero is busy trying to pull Asta towards a wall of the treasury. The said wall brandishes a similar locking mechanism that the was installed on the door to the treasury. Unable to understand Nero's hint, the anti-bird begins to peck Asta's head.

Not long after, Mars storms into the treasury and a fight ensues where the Diamond Kingdom mage manages to send Asta flying through the wall that Nero just showed him. Inside the hidden room, Asta discovers a sword that Nero was hinting about as the anti-bird lands on top of it. The former immediately reaches upon the sword and uses it to defend Mimosa Vermilion who is being occupied on healing Noelle Silva while Luck Voltia, Klaus and Yuno is trapped within Mars' spell.

During the fight, Asta is accidentally able to activate the sword's abilities as it absorbs Noelle's magical power. When he swings the said sword, a stream of water is released and manages to douse Mars' fire-based healing spell. Unfortunately, the attack is not strong enough to repel all of Mars' attack as Asta received a critical injury from his opponent's attack.

Seeing his rival is in danger, Yuno quickly breaks out his binding and tries to help him. Unfortunately, the latter does not possess a spell that could help Asta before Mars lands the killing blow. Refusing to give up, Yuno's surrounding becomes motionless and he find a girl with a pair of wings right by his side. The girl then blows a gust of wind that manages to inflict devastating damage to Mars, rendering him unconscious.

Once everything is over, the girl disappears and the writings that Yuno found within the scroll are now recorded inside of his grimoire. Subsequently, Asta's newfound sword also enters his grimoire with a series of writings also appearing in its place.

Epilogue
Afterwards, the dungeon begins to collapse. The positions where the sword and the scroll were located are the initial points of rupture. Yuno immediately creates a vessel for them to leave while Luck carries Asta to it for Mimosa to begin his healing process.

After failing to bring Mars with them, Yuno quickly directs the vessel towards the exit with the help of Luck's guidance. At the same time, Luck is also working together with Klaus to prevent falling debris from damaging the vessel. Once outside, they locate a safe place for Mimosa to concentrate on healing Asta until the boy regains his consciousness.