| Category | Strongholds |
| Location | Tarelcil |
| Owner | Arch-Mages of Merioss |
| Built | 15 Brightstar 68 |
| Map | Adellum |
The Prism of Merioss, commonly referred to as The Prism, is an ancient, magical castle situated atop the isle of Tarelcil. It is constructed upon a stationary air mote, a unique type of air mote, which supports the castle's weight. The Prism serves as the headquarters for a guild of powerful wizards known as the Arch-Mages of Merioss, who are tasked with protecting the Lands of Purity. The Prism's defenses proved formidable, resisting all assaults during the Black Tide War that spanned from 1465 to 1486.
The mages of the Prism are renowned for wielding immense power in times of great peril within the Lands of Purity. During the Athenian Crusade ( 1539 - 1551 ) , the island's sorcerers pooled their magical prowess to construct a potent lens atop the central spire. Each morning for one hour, this lens generates a vibrant rainbow stretching the expanse of the Galathien Sea. This phenomenon, known as the Rainbow of Tarelcil , instilled hope and the promise of a new dawn with the impending defeat of the Black Tide of Thasmudyan. Additionally, a properly trained wizard can traverse the rainbow's length at remarkable speeds in any direction.
In the Prism of Merioss lie numerous magically sealed vaults. These vaults safeguard perilous creatures, articles, and relics of immense significance. The location was christened the Prism of Merioss for the glass portals in the towers that, when struck by the radiance of Merioss, enable transit to any analogously constructed entryway within the castle.