Powers: It can create complete silence, as well as remove things that are making noise
Captured in: Episode7: Sakura's First Attempt as a Thief
How it was captured: Silent had merged inside a painting at a museum. Sakura couldn't get close enough to it to seal it away without making noise. She used Shadow(and a flashlight) to cast her shadow over to Silent, and then she raised her sealing staff's shadow in the proper motions to seal Silent away.