The Ruins are located at 711W 1022S, roughly half way between Tarant and Ashbury in the Morbihan Plains. They are marked on the player's map after accepting the quest from Cassandra Pettibone to Steal the Elven Funeral Stone. Successfully completing this quest can also lead to acceptance into the Tarant Thieves Underground.
The entrance (point 1) is guarded by 4 Dark Elf Nobles (point 2) who are also surrounding the body of one Professor James (see below). You can fight the guards or bluff your way past them to gain entrance to the ruins. You can also rat out Mrs. Pettibone which botches the quest but does generate an amusing headline in the Tarantian.
Professor James can be interrogated using Conjure Spirit, and can even be resurrected.
Underground are an assortment of undead creatures and several treasure chests. The Funeral Stone is found at the far western chamber (point 3).