The Star Prisms

Star Prisms are the main plot element and the collectibles of Super Mario and the Star Prisms. There are 8 of them, with each one being held by Bowser's elite minions and even Bowser himself. Despite they don't normally do anything when collected, they give you strength in lore when used.

Lore
The Star Prisms are powerful artifacts that were formed to keep the balance of the multiverse and the balance of elemental energies. With the help of the prosperous Jewel Kingdom, they formed the Star Prisms at the end of the War of Elementals.

'“...after none of the sides managed to take each other over. All sides have gathered for negotiation and decided to live in the universe together, within a balance of locations. And to honor their accords, they have decided to create artifacts that would keep the balance of the multiverse...” - War of Elementals’ Dialects, the Aftermath  '

Each Star Prism had an unique power within, fueled by the powers of ancient demigods/gods, heroes and elementals:


 * The Star of Unity was shaped in a civilization aimed to unite everyone within their landmasses. Terra, the princess of that civilization, willingly gave her lifeforce up for this Star Prism; and the elementals of order and light took her lifeforce and empowered it with their energy.
 * It was formed with malachite and gained lighter colors with Terra’s lifeforce present.
 * It was kept in the Altar of Unity, located in the viridian plains near Mushroom Kingdom.


 * The Star of Drought was shaped in the deserts around the world, perfectly forged to include a memory of every desert. The Star Prism also contains the lifeforce of nine Egyptian Gods who chose to seal their powers inside to keep the formed sands in balance: Anubis, Osiris, Horus, Seth, Thoth, Amun-Ra, Geb, Nut and Nepththys.
 * It was formed with topaz, with its overall color turning to a lighter sandy hue of orange with the cycle of sands.
 * It was kept in the Altar of Drought, located in the deepest catacombs of a large pyramid, location changing from desert to desert thanks to its energy.


 * The Star of Seven Seas was shaped in the seven seas around the world, and the layers underwater. The Avatar of Water and the water elementals, with the help of mages that controlled the weather, were able to form its power from the eternal cycle of water and oceans.
 * It was formed with aquamarine, which shifts from different hues of blue and green; the two colors of ocean.
 * It was kept in the Altar of Seven Seas, occasionally changing locations around different water sources.


 * The Star of Everfrost was shaped in the icy snowlands and the cold mountains surrounding it. The Avatar of Ice and the ice elementals; with the help of Sapphires and Eskimos, have created the energy protecting the balance of cold, from absolute zero to sustainable cold.
 * It was formed with sapphire and gained lighter colors with the energy’s presence.
 * It was kept in the Altar of Everfrost, located in the secluded far snowlands.
 * The wrong usage of this power can divert the balance of cold in a terrible direction, creating an eternal, shocking cold. It was given the term: “Everwinter”.


 * The Star of Nature was shaped in the vast collection of forests and jungles covering the entire world and other realms. The energy within this Star Prism is a combination of different beings: Shamans, Nymphs and other supernatural beings such as nature elementals; held a great diversity of life within, making it the strongest Star Prism.
 * It was formed with emerald, gaining darker colors with natural energy.
 * It was kept in the Altar of Nature, located inside the Tree of Endless Life, the largest tree located in the largest forest-jungle network around the world. (Sylvan Woods)


 * The Star of Shadows was shaped in the darker, night-dwelling locations and realms. There were shadowmancers and shadow elementals, controlling the balance of light of dark at bay. But when they realized their power is too dangerous to be kept to living, they instead gave their powers to the energy that powered this Star Prism.
 * It was formed with amethyst, gaining darker colors with the shadows’ influential energy.
 * It was kept in the Altar of Shadows, located in the Ghastly Graveyard’s northernmost mountains, a place that directed the reflected light of the moon from the sun.


 * The Star of Sins was shaped in the Underworld, by the Avatar of Fire, fire elementals and the 7 Demon Kings. (These kings held a different sin that reincarnated every cycle and they had the Ten Commandments as their bodyguards.) Their combined powers kept the Underworld’s overall energy at bay, protecting their realm from the Unholy Realm beyond their visions.
 * It was formed with ruby, gaining the color balance of lava and brimstone cycling.
 * It was kept in the Altar of Sins, located in the capital city of Underworld. (Also had the sealed portal of Unholy Realm)


 * The Star of Crypt was shaped in the forsaken realms where death is absolute. Mages who mastered the death magic and the life magic formed their power together to create the energy sealed inside this Star Prism. It protects the cycle of life and death, making it the second strongest Star Prism of all.
 * It was formed with onyx, gaining a lighter shade of gray with the energy’s insertion.
 * It was kept in the Altar of Crypt, inside an abandoned temple containing the embodiments of life and death itself, located in the forsaken realms.

"If all of the 8 Star Prisms were brought together and placed on the seals of Prismatic Gate, they could bring down the barrier in between four primordial forces and unleash the Realm of Discord. To prevent this, only the ones with sheer willpower and balance of emotions can use them up to their full potential and decide on the fate of the entire multiverse…”  - Erazor, the Guardian of Exordium [1]

In-Game
The Star Prisms are collectible items that are found at the end of each world, guarded by an elite minion of Bowser.


 * Star of Unity is in Viridian Grasslands (Guarded by King Bob-omb)
 * Star of Drought is in Dryrock Dunes (Guarded by Tutankoopa)
 * Star of the Seven Seas is in Tropical Beach Island (Guarded by Gooper Blooper)
 * Star of Everfrost is in Shivering Snowlands (Guarded by Crystal King)
 * Star of Nature is in Sylvan Woods (Guarded by Naval Piranha)
 * Star of Shadows is in Ghastly Graveyard (Guarded by King Boo)
 * Star of Sins is in Volcanic Lavalands (Guarded by Bowser)
 * Star of Crypt is in Restless Metropolis (Guarded by ???)

In order to acquire each of the prisms, the boss guarding it has to be defeated.

Trivia

 * The Star Prisms used to have a much larger role in the series, before gspezi14 stepped in and influenced the Prismverse's direction for the better.
 * The older plans featured the artifacts returning multiple times.