The Chysulan Chamber is a draconic artifact that was a pocket universe in itself, designed for varied purposes depending on which dragonflight had created them. But first and foremost, it was used for imprisoning magical creatures by drawing on the prisoner's own magic to keep the latter imprisoned. However, the Chrysalun Chambers had a few weaknesses. Firstly, they required alot of effort to to create and use, so, there were few of these around. even then, many of the chambers were unstable and flawed.
Lady Sinestra used hers to capture a nether dragon flying around the Dark Portal for her experiments. She later used it to trap Korialstraz in it to keep him from meddling with her plans and also for storage before she uses his energy to create more Twilight Dragons.