This is the 11982nd most frequent French word.
terrifiée
Terrifiée: Terrified; extremely scared.
The word "terrifiée" is used here as an adjective in the past tense to describe someone's emotional state, associated with fear towards a subject, in this case, the darkness.
Elle était terrifiée par l'obscurité.
She was terrified of the darkness.
Here, "terrifiées" is the same adjective, but in plural feminine form, indicating multiple subjects experiencing fear concurrently.
Nous étions terrifiées en entendant le bruit étrange.
We were terrified upon hearing the strange noise.
In this case, "terrifiés" is the plural masculine form of the adjective, used to describe a group mentioned in the sentence and their source of fear.