Hello, Tim ...
It is obvious that you enjoy both factual and fantasy history.
As we all know, the "Narwhal" is probably the origin of the Unicorn stories.
But, what if the Unicorn was really the ancestor of the Narwhal?
What if all the Unicorns actually only lived on the continent of Atlantis? And, when it sank during the last Great Global Warming (or whatever), the Unicorns survived by becoming Narwhals like the Humans who became Mermen and Mermaids?
I can just visualize this fantastic new theme from Playmobil. It would, of course, have to be set in Jules Verne's Victorian Period!
Now that would be something to see!
All the best,
Richard
(edit: misspelled "theme")