The Duergar was extremely frightened, but he only showed a look of confusion when he heard Marvin's request.
He couldn't understand Marvin!
Marvin felt a bit embarrassed.
He used Common, but while Common was spoken quite widely on the surface, those that lived in the Underdark generally used a lingua franca of their own, which he hadn't ever learned before.
Luckily, although he didn't know how to speak it, Jessica was pretty proficient in it, as she had been fighting in the Underdark for quite a while.
Marvin grabbed the pitiful Duergar and brought him to Jessica.
She was at a huge public square. From the buildings that surrounded it, the area looked like the place where the Duergar would hold celebrations and other various kinds of activities
"Who are you? What happened here?" Jessica asked in a threatening tone.