Learn French: Accablé par la chaleur, l'homme a dormi derrière la dune. - Overwhelmed by the heat, the man slept behind the dune.

This is a detached participial phrase. By putting the past participle Accablé at the start, it acts as an elegant shortcut to express cause and effect without needing a conjunction like parce que (because). It implies the meaning: Because he was overwhelmed by the heat, the man slept.

Does the word Accablé change depending on who is sleeping?

Yes, because it functions as an adjective here, it must agree in gender and number with the subject of the main clause, l'homme. If the sentence were about a woman, it would be spelled Accablée par la chaleur, la femme... and for a group of men, Accablés.

Could I use fatigué instead of accablé here?

You could, but accablé is much stronger. It means overwhelmed, oppressed, or weighed down. It is very commonly used with intense weather conditions, grief, or heavy burdens, making it the perfect word for the crushing effect of extreme heat.

Why do we use the preposition par after the participle instead of de?