The Shipwrecks of Ythaq T07 - The Mark of the Ythes

A luxurious cruise vessel crashes on Ythaq, a planet which, curiously, isn't listed on any chart.
Among the survivors, a young and intrepid astro-navigator, a poetic technician and a beautiful passenger. stalked by pitiless mercenaries, they are going to discover a medieval world where many different species live together in amazing harmony. But, are the shipwrecks accidental? What terrible secret is hidden behind the walls and the doors of the palaces of Ythaq?