| Category | Strongholds |
| Location | Tarelcil |
| Owner | Arch-Mages of Merioss |
| Built | 15 Brightstar 68 |
| Map | Adellum |
The Prism of Merioss, or simply The Prism, is a very old, magical castle sited above the isle of Tarelcil. It is built on a type of air mote that is stationary and supports weight. The Prism is home to a guild of powerful wizards called the Arch-Mages of Merioss. They serve as protectors of the Lands of Purity. The defenses of the Prism are formidable and resisted everything that was thrown against it in the Black Tide War (1465 - 1504).
Those of the Prism are known for coming forth in great power when the Lands of Purity are in great danger. During the Athenian Crusade (1539 - 1551), the mages of the island pooled their magic to create a powerful lens atop the central spire. Every morning for one hour, this lens creates a rainbow that stretches the length of Galathien. This effect became known as the Rainbow of Tarelcil. It was created to give hope and a new dawn that shall come with the defeat of the Black Tide of Thasmudyan. The other aspect of it is that a properly trained wizard can use it travel the rainbow in any direction.
In the Prism of Merioss are many magically sealed vaults. These vaults hold dangerous creatures, items, and relics of great importance. The place was named the Prism of Merioss for the glass doors in the towers that when struck with the rays of Merioss, allow travel to any similar constructed door within the castle.