The Lanten Family Mausoleum was the final resting place of Bander Lanten -- the patriarch of the Lanten family line -- and generations of his descendants.
It had more recently been taken over by Nevin and his group of orc henchmen, who are all somehow tied to an organization that uses a red skull sigil to identify themselves. They were using it as a holding place to keep captives until they were ready to be sent to the mysterious "Witch-Queen" as slaves.
The party was freed from their captivity one night when Vonder and his two thugs, Harwin and Tud, broke into the mausoleum with the intentions of robbing the graves. The vandalism they inflicted on the upper floor ultimately led to the collapse of the entire building.
The Lanten Family Mausoleum is no more, now just a pile of rubble at the foot of a high cliff wall.