Vikings

We are constantly experimenting with new technology and you are mistakenly stranded in the Lord's year 966. To get back to the present, you need more energy crystals for your time machine. You have heard that the Viking chief Erik the Red hides crystals in his fortress. He's off on a train, but you can already see his ships on the horizon. Erik and his men rarely welcome unexpected guests - and they're going ashore in an hour... Can you manage to find the energy crystals before the Vikings come?