Game of Thrones edited out a lot of characters/stories from books like Lady Stoneheart (which is discussed here) and even shortened the stories of a few characters like Cold Hands (which is further discussed here). And same the happened to many Dorne characters and story arcs.
But one character who had a significant story in the Dorne arc in the book did appear but is never called by that name and didn't even show his face.
His task is to protect Myrcella Baratheon in Dorne but even after
the death of Myrcella Baratheon
he didn't even show his face. What was the reason for not showing his face? Did they even cast anyone for that role or was it always played by some random extra?