Rationally thinking, that would make sense.
The pen moved by itself.
Could it be an 'animate object' spell?
Is someone holding and moving the pen with 'invisible hand' magic? No, surely not such common and simple magic.
Or telekinetic control from afar... then there might be magical devices watching and listening inside this room. Maybe familiars hidden in insects or rats.
Obern's head spun.
There was only one certain countermeasure he could take right now.
Block magic.
Yes, he had artifacts for that at least.
As much as he lacked confidence in his own ability, Obern was obsessed with artifacts.
He twisted a cubic cube taken from his chest, and it split into four pieces.
Obern scattered those pieces to the four corners of the room.
Clatter-
A barrier blocking magical interference.
