From Destinypedia, the Destiny wiki
Dreadnaught, Saturn's Rings
TakenThe Silent Brood
The FountsThe Hanging Crypts
The Asylum is a location within the Dreadnaught orbiting Saturn.
The doorway past where the player fights Primus Ta'aun and Baxx, the Gravekeeper can be scanned by Ghost. Ghost claims that behind that door, which leads to The Hanging Crypts, are things even the Hive fear, and have not yet been able to weaponize.