During the dark ages (early middle ages), the Vikings visited an isle surrounded by strong waves and giant whirlpools that seemingly appears sporadically. The island is populated with many walrus and there is also a cavern covered in abundance of silver and iron ore. Unfortunately, it is also a lair home to a 25m long thunder wyvern measuring from snort to coccyx with a wing spans of 100m when fully extended. During the day, the island will be covered in a thick fog and miasma. The effluvia seems to be both corrosive and poisonous to most living things except the wyvern. Therefore the Vikings had to wait until nightfall when the fog and the miasma dissipates, and the nocturnal wyvern comes out of its lair to hunt. The thunder wyvern got its name from the deafening and piercing screech it emits as well as the sighting of hundreds of ball lightnings that seemingly pop out of nowhere every time the creature spreads its wings before it takes off from the ground! A typical lightning ball can release up to 300,000,000 volts of electricity and is about 30,000 Amperes. As soon as the lightning ball appears, the surrounding air around it starts sparkling and explodes with a force of 0.12 tons of TNT with a wide radius of 5m. The richness of the island is too lucrative to pass up. I am wondering how can the Vikings defeat the thunder wyvern for good?
Vikings's wishlist: Red meat, Ivory, Leather, Silver, Iron, Trophy, etc.