Beautifully animated and compelling, the Celtic fantasy series scratches a "Scooby-Doo" itch cartoons have been missing. This story first ran in the  animation  newsletter “ Sketch to Screen .”  Subscribe here  to receive a new entry every Thursday. Few premises are as eternal or as durable than a group of friends solving mysteries: Hanna-Barbera practically made an entire genre of it in the ’70s, taking the premise of the classic “Scooby-Doo” and xeroxing it for a dozen other shows. And yet,