It was a massive, flying fortress designed by Belthasar and commanded by Dalton. Before the Kingdom Zeal is destroyed by Lavos, the Blackbird's mooring place can be visited. However, the airship cannot be boarded.
When the Kingdom of Zeal was destroyed by Lavos, Dalton commandeers it and tries to use the Blackbird to re-establish the rule of the Enlightened Ones over the Earthbound Ones, with himself as the new king. The party is captured and taken to the airship, with their weapons, items, and money was stolen. They escape from the prison to find that Dalton added wings to the Epoch. They reclaim their belongings by climbing through the ventilation system. They then jump onto the Epoch and battle Dalton. After regaining control of it, they accidentally destroy the airship with the lasers Dalton installed.
Helpful Tips for Beating the Blackbird