Eel cage

An eel cage is an underwater torture device in which four electric eels are restrainer by a set of binders to create a restraining device. The prisoner is placed inside the cage, and the electricity created by the eels prevents them from leaving. If the interrogator forces one of the eels inward, it strikes the prisoner and sends a painful electric charge surging through them.

During a Clone Wars battle on Dac in 21 BBY, Riff Tamson placed the Jedi Anakin Skywalker and Kit Fisto inside eel cages while trying to learn the whereabouts of the Mon Calamari Prince Lee-Char.

Behind the scenes
The eel cage first appeared in the Star Wars: The Clone Wars episode "Prisoners". Although not identified by name during that episode, they were described by the name "eel cage" on concept art that appeared on the official StarWars.com website after the episode first broadcast.