The legal ability of states to secede

In the context of the United States, secession primarily refers to the withdrawal of one or more States from the Union that constitutes the United States; but may loosely refer to leaving a State or territory to form a separate territory or new State, or to the severing of an area from a city or county within a State.

"divine intervention"

While King Arthur and the quest for the holy grail has very little to do with history and was actually a story. FYI

The image of the holy grail appeared above the round table and this was taken as a sign that they needed to go find it