The Planispheric Disk was used by the Spanish Conquistadors to navigate unknown waters, or to hide their cargo. There is one in Crystal Cove that has been divided into pieces and the pieces are sought after by several factions (Professor Pericles, Fred Jones, Sr., and Mr. E). The disk is supposed to be a key to finding the Cursed Treasure left in or near Crystal Cove by the conquistadors.
The original conquistador, Fernando El Aguirre, used the disk to mark the spot where he buried a crystal sarcophagus filled with black pearls that he stole from a temple somewhere in Central America. He later broke the disk apart to make sure no one knew where it was. The Spaniard had two pieces with him, but before he descended into madness the two pieces made it into the hands of some mystery solving Franciscan monks, the Fraternitas Mysterium.
The monks, feeling the dark power of the disk, wanted to destroy them or at least hide the pieces. Their mascot donkey Porto was corrupted by the evil of the disk. The donkey blew up the area using powder kegs, hoping to keep the piece to himself. This act caused a great earthquake which caused most of the original mission settlement to slide into the sea. Friar Serra pursued the escaping donkey, and got the stolen piece back; Porto was apparently devoured by the alligators of what would one day be Gatorsburg. Friar Serra hid the piece he recovered in a wheel of cheese. Another piece was lost in the sunken town. The pieces then fell into obscurity, scattered over the globe.
A new group appeared in the 1880's, led by Oswald P. Burlington with his orangutan Mr. Peaches as a mascot. One of their members, Abigail Gluck, managed to scour the remains of the lost city in the sea with her robots, but she died in her underwater lair before she found the lost piece.
A piece eventually came into the possession of the Darrow family, who formed their own mystery-solving group. This lead to major tensions within the family and the death of most them except little Danny Darrow. He kept the piece hidden away in his mansion which had sunk beneath the ground, becoming obsessed with it.
The original Mystery Incorporated (with Professor Pericles) found one of the pieces in the Old Spanish Church and investigated the former Darrow Mansion. (Danny Darrow watched them and wanted to trap them, but he failed to build his traps in time). They broke up because of the treachery of Pericles and threats against their parents by the Freak of Crystal Cove.
Scooby-Doo! Mystery Incorporated
The legend of the disc was heard by the current Mystery Inc., so they also entered the former Darrow mansion but were successful in gaining the piece after talking to Danny Darrow. The next piece was in Mayor Jones's safe, which Professor Pericles managed to steal for his own gain.
The third piece was discovered by Hot Dog Water and Velma Dinkley inside Baba Yaga's house, which they bought from the Russians as agents of Mr. E. The fourth piece was found inside the wheel of cheese the monk hid it in, which wound up in a traveling side show. The fifth piece was found on the original Spanish ship and was guarded by many traps. Mystery Inc. managed to get through and gain the piece, after it was briefly stolen by Dark Lilith. The final piece was found in the underwater city, and Professor Pericles stole it.
The battle for the pieces ended when Mystery Inc., with some old enemies turned allies, managed to gain all the pieces and put the discs together.
Velma managed to create a machine to read the disc but one word appeared and it was "Nibiru".
The mummy-ghost of Friar Serra, who hid the disc piece inside the cheese, warned the current Mystery Inc. that the animal is the first to start the downfall, and "The dog must die!".
- Scooby-Doo! Mystery Incorporated