This is such a cool episode that has always been one of my personal favourites.
When Ulysses comes across a planet (that is home to a band of pirates), they capture him and force him to travel to find the Sirens' treasure and bring it back to them.
The Sirens are really cool, with their haunting singing and echoing whispers "Come...Join us". To combat this, Ulysses uses ear plugs to try and resist them, but he dives in...
The treasure of the Sirens is actually the map back to Earth, but is protected by a strange twin horned thing that can turn people to stone, as it did with the band of pirates.
Unfortunately, the map dissolves when activated.
The incidental music throughout this is so cool, if only I could find it on CD.