A word or phrase that implies "a struggle or hardship is about to begin"? [closed]

Looking for a word or phrase that embodies the feeling of "the struggle is about to begin". Can be a borrowed/loan word or phrase from another language (Latin, French, etc). It should have the feeling of something is about to happen, something unpleasant that will be taxing on the individual.

I am planning to use this phrase in a story, in which a struggle is about to begin.

A few idiomatic examples:

• The die is cast.
• Caesar has crossed the Rubicon.
• Hannibal has crossed the Alps.

The first two idioms refer to the same event. From Wikipedia:

With this step, he entered Italy at the head of his army in defiance of the Senate and began his long civil war against Pompey and the Optimates. The phrase, either in the original Latin or in translation, is used in many languages to indicate that events have passed a point of no return. It is now most commonly cited with the word order changed ("Alea iacta est") rather than in the original phrasing. The same event inspired another idiom with the same meaning, "Crossing the Rubicon".

More colloquially, you could say the shit has hit the fan.

Fasten your seat belts

In the most famous line from the 1950 movie All About Eve, the character Margo Channing (played by Bette Davis) said

Fasten your seatbelts, it’s going to be a bump-y night!

"Night" is often replaced by the more sensible "ride".

As anyone who has been in a plane has experienced, a "Fasten Seat Belts" sign comes on when the pilot has to make a difficult maneuver, or if the plane goes through turbulence.

So most people will understand that some sort of turmoil is expected if you say "Fasten your seatbelts". But it's often used jocularly, as if the difficulty is trivial or survivable.