Learn Spanish (Latin America): Hacía horas que la desesperanza dominaba su mente. - Despair had been dominating his mind for hours.

In English, we use the past perfect continuous ('had been dominating') to show an action started in the past and continued up to another past moment. In Spanish, when you state the duration of an ongoing past action (like horas), you use the structure hacía + time expression + que + imperfect verb. Because the despair was still dominating his mind at that narrative moment, we use the imperfect dominaba.

How would this sentence look if the despair was still dominating his mind right now in the present?

You would shift both verbs to the present tense: Hace horas que la desesperanza domina su mente (Despair has been dominating his mind for hours). Moving the narrative to the past simply requires shifting hace to hacía and domina to dominaba.

Could I put the time expression at the end of the sentence instead?

Yes, you can invert the structure. You could say La desesperanza dominaba su mente hacía horas. Notice that when you move the time expression to the end of the sentence, you must drop the connecting word que.

Why is there a la before desesperanza when the English translation is just 'despair'?