Device used by the Goa'uld, capable of completely restoring the physical form of an individual placed inside -- even potentially bringing them back from the dead. However, while restoring the flesh, the mind is manipulated, often with dire consequences. The Tok'ra refuse to use the sarcophagus, believing that it drains the good from one's soul.
The first sarcophagus was developed by the Goa'uld Telchak thousands of years ago, after he found the powerful Ancients healing device. The sarcophagus uses a similar, but less powerful form of the energy emitted by this technology. Anubis went to war with Telchak over the original Ancient device, but it was hidden away on Earth