The return of Excalibur to the world awakened forces that normal mortal minds found difficult to comprehend. The change was slow at first: a reappearance of the fey here, a sighting of a ghostly knight there. Most people thought them the tales of late night drunks or hallucinating drug addicts. So no one was prepared when the crown forests exploded, spreading greenery across the whole of the island.
The resurgence of magic quickly spread, ripping up and replacing modern technology with its own brand of strangeness. Some technology survived somewhat intact, seemingly entwined with magic at it's core, such as the crystal computer at the lighthouse at the old Braddock mansion. Other technology was replaced by what came to be termed its "esoteric equivalent". While this presented mild consternation for your average army that now had bows and crossbows instead of MP-5s, it caused a much greater concern at air force bases that now had to feed flights of tame, but cantankerous, dragons.
Returned from Avalon, the Lady of the Lake appeared to everyone on the island, her face hovering over every substantial body of water. "Now that I and my kin have returned, we want you to know that you are not defenseless against the worst of our kind. Among you there are those who have been given a great gift. The blades of old that have been held away from this world have been returned to new wielders. Once those are found, the Round Table may be built anew and those with the will to be heroes will have their seat there."
As her address finished, the Houses of Parliament shimmered and glowed, transforming into a large castle with a clock above the moathouse. Everyone inside at the time magically appeared outside the building. Attempts to reenter proved to be impossible as the doors refused passage for all who tried.
Life began to move on. Some people claimed to have one of the swords that the Lady of the Lake had spoken of, but all were proven false by their inability to enter the 'Big Ben Castle' as it came to be called. Rumors persist that the Lady of the Lake was just toying with the mortals as her kind tend to do. Others say that the blade wielders do exist and that we do our best to stay hidden, because the day that the Round Table is needed has not yet come. Whatever the reason, the days are drawing close when we will have no choice to reveal ourselves and then the Round Table will be filled again. Even now I can feel the pull of that place, calling to me through the sword...
- Tereza Rozanov, Wielder of Frostbringer
Characters don't have to be one of the sword wielders, but are welcome to be. That's why I purposely left the number and nature of the swords themselves nebulous. In general, magic is the order of the day and for some reason, modern technology largely ceased to function. So it was an apocalypse of sorts, but a fairly tame one. Some characters may have had their abilities or appearance altered as a result of the magical resurgence. For those that have figured out the rules of magic, it is possible to replicate some of the old (like using magic to talk at a distance between two bowls of water).