Crumbled human remains.
In Chapter I in the Outskirts Inn, Geralt meets Declan Leuvaarden, a rich merchant, who asks the witcher to find his missing companion, or failing that, his remains and to give them a "decent burial". The remains of Leuvaarden's companion, initially described as merely "crumbled human remains", are within the Outskirts. In fact, they can be found in an echinops-infested cavern just west of the Maribor Gates to the city of Vizima.
Once recovered, there remains the matter of the "decent burial". Here, the Reverend comes to the rescue and offers a "crumbling sarcophagus" in the crypt beneath the Chapel.