The Prison Dimension is Exactly What It Says on the Tin: Another Dimension that is largely used for the sole purpose of imprisoning someone or something. Has shades of Pocket Dimension and Tailor-Made Prison. See also Phantom Zone.
Examples of this trope include:
Live Action TV
Arcanum: Of Steamworks & Magick Obscura: An ancient Evlen council used to dump the most powerful villains into dimension called the Void instead of simply executing them, since it is possible to return Back from the Dead, but not from the Void. The plot point is that one of the banished is going to return anyway...