In 'The Legend of Ragnarok, a spate of local seaquakes has citizens of Berk remembering a long whispered tale of a huge monster that will one day rise from the sea and end the world. In 'Underworld', Hiccup and his friends discover a huge, mysterious pit in a forest near Berk while Stoick investigates a number of fishing vessels that have gone missing - but, little do they know, the two events are connected.