|Origin||The Little Mermaid|
|Games||Kingdom Hearts III: Vengeance|
|Keyblade Wielders||Master Xehanort, Vanitas|
|Theme Music||Night of The Dark|
|Battle Music||Night of Tragedy|
Once called Atlantica, this beautfiul ocean world was invaded and corrupted by Primoris Carmina. He enslaved the mer-people, and seized control of of their king's Trident, using its power to control the world's oceans and use it against any and all intruders. Eric's castle was turned into his and Master Xehanort's fortress,a massive tower of twisted black metal, guarded by armies of the most powerful and deadly of heartless.
It was soon established as the base of operations for Xehanort's group of villains, as they planned to obtain the power of Kingdom Hearts. Primoris called their new lair, and their conquered world, Diabolus Arcem, a latin phrase meaning the "Devil's Citadel".
Kingdom Hearts III: Vengeance
A once lush and beautiful undersea kingdom thrived on this world. Upon its takeover by Primoris and Master Xehanort, most of the fish were killed by toxins and pollutants that poured into the oceans, upon the construction of the villain's massive citadel. Triton's palace was crushed by armies of undersea heartless, and turned into an underwater outpost. From here, the villains monitor any underwater activity, such as locating intruders, or overseeing the enslaved oceandwellers.
Most of the coral reefs, caverns, casyms, all of them have been wither demolished in the constuction of weapons for defense of the citadel, or for energy purposes like underwater oil wells, or geothermal energy generators. And as for the toxic oceans themselves, they are in a constant state of hurricane-like winds and waves, thanks to Primoris wielding King Triton's trident. Keep in a special chamber, Primoris feeds dark energy into it, to make the surrounding oceans turbulent and deadly to any intruders.
The land on the surface was not better. The green countryside has been corrupted and turned into rocky cliffs populated with watchtowers, gun turrets, energy nodes, security sensors, and factories that create the armies of heartless. The ground has become like smooth, black, molten rock. Red weeds dominante the remaining flora, and are poisonous to anything but the Heartless.
Sora and his Company recons the fortress, that Donald, Goofy, and his friends gave the mission. Sora and Company got to watch out for gun turrets, missiles, and some Pureblood heartless carrier ships, but the blockades everywhere, the Heartless Soldiers battles against the heroes, and fight for glory. However, Max goof, aqua, and several heroes infiltrate the lair, and find King Triton's Trident.
Fiercely, Primoris enrages the dark electrical lasers to attack sora. Master Xehanort is erupted the city to face-to-face against sora. Riku finally got the Trident to restore the undersea kingdom. Both Xehanort and Primoris was finally destroyed, and the armies of heartless falls into extinction. The Security sensors, and some watchtowers suddenly disappeared and the rocky cliffs returns into green countryside, and then all toxins and pollutants poured into the oceans that vaporized and eradicated into blue water.
The Villain's Massive citadel was reverted back into triton's palace, and then, Diabolus Arcem was totally Vanished, and was reverted back to atlantica.