game of thrones - Does Maester Marwyn exist at all on GoT planetos?

Currently there is no Maester Marwyn in the TV Show. Even in the books we don't know for sure what role Maester Marwyn would play, but it looks increasing likely

that he could convince Daenerys Targaryen to come back to westeros.

Game of thrones TV Series hasn't introduced a lot of characters we read about in the book but it looks likely that the TV Show could run for 8 seasons so there is still hope.

"Seven-seasons-and-out has never been the [internal] conversation. The question is: How much beyond seven are we going to do?"

"Obviously we're shooting six now, hopefully discussing seven. [Showrunners David Benioff and Dan Weiss] feel like there's two more years after six. I would always love for them to change their minds, but that's what we're looking at right now."

Already two new cast members have been added Max von Sydow most likely as the Three-Eyed Raven and Ian McShane as yet to be confirmed character. He might take up the role of Marwyn but again Maester Marwyn may not even appear in the TV Series.

There are statements by Maester Marwyn which points to the fact that he could play a important role in the story.

“Did he?” Archmaester Marwyn shrugged. “Perhaps it’s good that he died before he got to Oldtown. Elsewise the grey sheep might have had to kill him, and that would have made the poor old dears wring their wrinkled hands.”

“Kill him?” Sam said, shocked. “Why?”

“If I tell you, they may need to kill you too.” Marywn smiled a ghastly smile, the juice of the sourleaf running red between his teeth. “Who do you think killed all the dragons the last time around? Gallant dragonslayers armed with swords?” He spat. “The world the Citadel is building has no place in it for sorcery or prophecy or glass candles, much less for dragons. Ask yourself why Aemon Targaryen was allowed to waste his life upon the Wall, when by rights he should have been raised to archmaester. His blood was why. He could not be trusted. No more than I can.”

_{^{A Feast For Crows}}

We can cross our fingers and wait for the next season.