The Dyna Stones are really powerful weapons from the One Piece universe, specifically made for the non-canon movie "One Piece Movie: Z". The mysterious objects of unbelievably explosive nature are supposed to be among the aces from the trump card collection of the Marines, and their power of destruction is said to be reminiscent of ancient weapons of the One Piece world.
The appearance of the Dyna Stones is quite unique physically. They are represented by ovoids floating in a pink liquid within some sort of mysterious chamber. The visuals only enhance their enigmatic nature and drive home that they form an important plot device for the movie.
The most striking feature about the Dyna Stones is that they are explosive in nature. When exposed to air, these stones create explosions of immense destructive power. This property makes them incredibly dangerous and a coveted weapon for those who wish to cause large-scale destruction.
The plot of "One Piece Movie: Z" revolves around Dyna Stones. They are stolen by the movie antagonist, Zephyr—a former admiral in the Navy turned pirate. He would create the main conflict for the film by having a confrontation with the Straw Hat Pirates and the Marines through the theft of Dyna Stones.
The introduction of the Dyna Stones in the film raises the level of the conflict. Their power will be so great as to equal the Ancient Weapons, mighty and perilous items within the world of One Piece. This helps frame the threat level of the Dyna Stones for viewers familiar with the lore of the series.
It is important to note that the Dyna Stones are not canon material within the original One Piece storyline. They serve mainly as a plot device for the movie "One Piece Movie: Z" and do not appear in the manga or anime series at all. In this regard, they share their status with a lot of other elements from One Piece movies, which frequently introduce some unique weapons or powers that are never referenced within the main storyline.
Even though they are non-canonical, the Dyna Stones have appeared elsewhere in other media related to One Piece. In the video game One Piece World Seeker, for example, Dyna Stones are said to exist on the same island as in the setting of the game, with ancient texts said to exist alongside it that pirates are interested in; this exemplifies how movie elements can be used in other areas of the One Piece franchise, even if they do not affect the main storyline.
The concept of Dyna Stones enriches an already rich tapestry of powerful and dangerous objects in One Piece. It is part of the world in which the main series focuses on Devil Fruits and ancient weapons, and further lore with Dyna Stones in this movie is added to pose a new threat for the characters to engage with.
In "One Piece Movie: Z," the Dyna Stones are much more than a weapon. They represent the symbolism of military power against itself and the dangers when weapons get into wrong hands. This theme fits into larger tales in One Piece about the balance of power and good versus evil within powerful organizations like the Marines.