A 'Harry Potter' actor was just cast in 'Game of Thrones' season 7 - here's who he could be

Warning: Potential spoilers ahead for "Game of Thrones" season seven.

"Game of Thrones" has officially started filming, and we now have confirmation about the season's first new cast member: Jim Broadbent.

Entertainment Weekly reports Broadbent has been signed on for "Game of Thrones" season seven, and his role will be "significant."

Unfortunately, the information stops there. So who might Broadbent be portraying?

Our best guess is either a new religious leader - surely the High Sparrow had prodigies outside of King's Landing? - or a maester.

Sam Tarly just arrived in the Citadel, and last we saw he was waiting for the Arch Maester to meet with him. Since the Arch Maester is one new face we're definitely going to see, it makes sense for Broadbent to be stepping into his shoes. Plus he just has that "maesterly" look about him.

There's also a book character named Marwin the Mage, who embarks on a pretty important journey with Sam after meeting him in the Citadel. This would fit with the "significant" qualifier in the news from EW.

Broadbent could also be playing a smaller role, similar to Ian McShane's appearance in season six as Brother Ray. McShane only stuck around for a single episode - perhaps Broadbent is in for a short stint, too.

This isn't Broadbent's first appearance in a fantasy franchise. "Harry Potter" fans should recognize as Professor Horace Slughorn.

With season seven airing sometime in the summer of 2017, this is just the beginning of casting news and speculation.