Demiplane of Chains

Outside of the prison plane of Carceri, the Demiplane of Chains is one of the most secure prison sites in the multiverse. It is a demiplane in the Deep Ethereal, only about 6 miles in diameter, but filled completely with intelligent but non-verbal links of chain. It is widely believed the demiplane is alive, similar to the Engulfing Hunger, and that each chain link acts towards the central will of the plane itself. For all intents and purposes, that central will seems dominated with holding prisoner anyone or thing that enters its ethereal curtain. Angels, devils, sorcerers, warlords, and more have become trapped in the Demiplane of Chains.

Is there a way out? A legendary thief now hiding out in the City of Brass claims to know a way and he has the link of chain from the demiplane to prove it. Getting someone out of the Demiplane of Chains would prove a monumental task as the sentient links move like great metal serpents to ensnare and imprison anyone that enters.