Warning: This post contains potential spoilers for Game of Thrones' seventh season.
On Thursday, HBO confirmed to TIME that Jim Broadbent would be joining Game of Thrones in a "significant" role, marking the first major cast addition for season seven. Beyond that description, nothing else was revealed about the 67-year-old Oscar winner's role on the HBO drama.
But that didn't stop the people of the Internet from rising to the task of speculating and narrowing down the list of Westerosi residents he might play, with some Reddit users guessing that the most likely candidate is Marwyn the Mage.
In George R.R. Martin’s A Song of Ice and Fire series — the books on which Thrones is based — Marwyn is an archmaester (a high-ranking leader) of the Citadel who Sam meets when he arrives in Oldtown. However, he is unlike most maesters because he has a deep connection to magic and the supernatural that defies the common beliefs of his order.
He has traveled the world and spent several years across the Narrow Sea studying ways of living — including those of the shadowbinders and warlocks. In the books, he is also said to have been the one who taught Mirri Maz Duur — the priestess who Daenerys burns to death on Khal Drogo's funeral pyre after she betrays her with blood magic — the secrets of the human anatomy.
When Marwyn last appeared in ASOIAF, he was leaving Oldtown in search of Daenerys, so if Broadbent were to play the role of the archmaester on the show, it would be interesting to see in what stage of his journey viewers meet him.
Of course, because Thrones surpassed the plot of the books in season six, it is also possible that the role is for a completely new character that neither readers of the books nor viewers of the series have been introduced to yet.