"Let's start with the torture first and ask questions later, shall we? Hehe"
Eren removed a palm-sized pebble from his storage that had various inscriptions inscribed on it. He supplied enough of his unelementalized mana and the inscriptions lit up. Soon a semi-transparent dome with a 10m radius formed with him and the cultist in the centre.
This was the sound isolation artefact Eren was gifted with by Matt when he was in the city of Lauriel. The guy had come to the butcher to sign his death warrant with his own hands and blood. The butcher was just kind enough to grant him his request and accept this artefact as a payment.
"Sound isolation artefact? Little bastard, how many victims have fallen in your hands for you to carry this type of artefact on you? Don't tell me you were counting on me to attack."