Hook: Ceiling HookThe Cage of Tormented decoration fits into a purple ceiling hook.
How to Get a Cage of Tormented Decoration
Cartel Pack Decorations
The Cage of Tormented decoration can be dropped from Seneschal's Stronghold Packs, which were released on the Cartel Market and bought with Cartel Coins. Cartel Packs, including the Seneschal's Stronghold Pack, include a random selection of items from the Seneschal's Stronghold collection of items. You aren't guaranteed to get a Cage of Tormented decoration from a Seneschal's Stronghold Pack, but it is one of the few ways to get a Cage of Tormented deco apart from buying it on the GTN from another player.
If you're looking to get a Cage of Tormented, the easiest way to get it is to head to the Galactic Trade Network (GTN) in SWTOR and buy it with credits from another player. If it's very rare and not available on the Cartel Market, you could try buying from the GTN and hope you get it.