English Idioms and Phrases: The Die is Cast
Sometimes referred to as 'the die has been cast' means to have crossed the point of no return, meaning there will be an inevitable consequence for an event that has taken place.
"If it was a good thing to do or not, the die is cast and now we wait"
This phrase is closely linked with 'cross the Rubicon'. It is a Latin phrase attributed to Julius Caesar and is still in use today.
Die is the singular for dice and refers to gambling. When you throw, or cast a standard die, it will land on a number between 1 and 6. So as soon as you have thrown the die you have to wait to see the inevitable result.