It's been a while since the last time I visit this forum. Now I'm back… with some idea to storm your brain.
General Idea/Elevator Pitch
An 18th century French fortress/settlement named "Fort St. Marie-La Roche" that are isolated for hundreds of years and hostile towards everything within their radius.
Despites being outdated, their weapons (musket and pistol) are capable to penetrate modern military-grade armory. The human population of the fortress remain static, with its people are generally immortal and able to regenerate their wounds. Most of the population still shows loyalty towards the French monarch, even after the dramatic fall of the monarchy in France.
Central Narrative
Fort St. Marie-La Roche are constructed in early 1726 in the area now known as Newfoundland and Labrador. For several years, St. Marie-La Roche operates like a normal French Fortress and able to grow it's own town without any anomalous activity inside it.
The fortress are raided by British mortar in the Seven Years' War between French and British. After the raid, some personnel and population escaped the fort because.. well.. the forts are destroyed, but some choose to stay in the fort, including the Commanding Officer, Colonel Jean-Paul de Natalie. The fort lost contact with the French Navy and presumed destroyed by the government, thus forcing the commands in St. Marie-La Roche to act on their own.
St. Marie-La Roche remain unknown for years until the Royal Navy discovered the fort in 1935. The Royal Navy were quickly attacked by the fort's cannons and mortars, the ships have to retreat from the site in order to prevent further casualties. The acting captain immediately report it to the Admiralty, in which the Admiralty ordered further inspection and supervising. The Royal Navy continue to watch the fort with their patrol boat until 1940.
The RPC Authority are notified about the St. Marie-La Roche's existences in 1950s. The researchers are aware that St. Marie-La Roche are hostile towards everyone, therefore they're directed to keep safe distances from St. Marie's detection and attacking radius.
The first infiltration attempt were conducted in 1958, which resulted in two operatives being killed by the fort's personnel. After countless attempt and evaluation made by the Authority, they've decided to keep distances from the fort, considering the attempt of infiltrating and/or destroying is deemed
"not very worthy" and violates the Authority's value.
Why Shall I Care About This? AKA The Hook
I believe that from this small concept of isolated hostile fortress are able to be expanded into a far more wide story and able to be integrated into broader RPC Universe.
Notes
Rain me with your crits, this thing needs more improvement. Contact me in Discord (Coordilatte#9929) if you need to.