Castle Coeffin on the Isle of Lismore was built between 1200 and 1250 AD to guard the sea passages between Scotland's western isles. The castle became one of the strongholds of the MacDougalls, the Lords of Lorn, the enemies of the Macdonalds, the Lords of the Isles. Both clans were descended from the Norse-Gael Somerled who forged the Kingdom of the Isles. (You can read his story in the award-winning story, Summer Warrior, book 1 in the Clan Donald Saga.) 
See the book on my website.

Lismore Isle became a point of contention between the two clans in the late 13th century. Alexander Macdonald, heir to the Lordship, fell in love with and married Juliana MacDougall. Her dowry was to be Lismore Isle where Castle Coeffin then stood. But Alexander MacDougall, the MacDougall clan chief, reneged on his promise and denied the dowry.

Ultimately, King Edward I of England would decide for the Macdonalds. You'll be able to read about it in the story I am writing now, Bound by Honor, coming later this year.
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Geddes MacGregor once wrote, “No one in Scotland can escape from the past. It is everywhere, haunting like a ghost.” Scotland’s past is the subject of this list, romance novels set in Scotland, most in that magical part of Scotland called the Highlands. Some have a Scot as hero or heroine. The best are set deep in Scotland’s history.
See the list here: https://reganromancereview.blogspot.com/2021/05/best-scottish-historical-romances.html