The castle could've hosted Islamic Commanders convening with Scottish Commanders talking strategy.
Vikings traded with Islamic countries and some of their jewelry was found in Viking tombs dating back to the 12th century. Maybe some Scottish merchants did too?
xmarketladyx t1_it5wvti wrote
Reply to Researchers look to unravel story of Islamic glass found in Scottish castle - HeritageDaily - Archaeology News by GullyShotta
I mean, it's not that difficult: