Through its first four seasons, HBO’s “Game of Thrones” has been a fairly faithful adaptation of George R.R. Martin’s “A Song of Ice and Fire” book series. But that may soon change as the show enters its fifth season – premiering Sunday – and begins to catch up to the published novels. Before the series ventures where no book has gone before, we took a look back at the biggest differences between the show and the books so far.

Here are the nine biggest divergences between “A Song of Ice and Fire” and the first four seasons of “Game of Thrones”:

1. Character Ages

The age of many key characters is very different on the show. In the first book Robb Stark (Richard Madden) and Jon Snow (Kit Harrington) are 14, Sansa Stark (Sophie Turner) is 11, Arya Stark (Maisie Williams) is 9, Bran Stark (Isaac Hempstead-Wright) is 7 and Daenerys Targaryen (Emilia Clark) is 13. Every one of those characters was aged at least five years in casting – understandable for television, given the explicit subject matter featured on the show.

2. House of Undying

Some of the more contested differences for fans were the alterations in the visions experienced by Daenerys when she visited the House of the Undying in Qarth in Season 2. In the books, Daenerys sees much more literal scenes of both the past and, presumably, the future. On the TV show her visions are much more cryptic, including one where she sees her dead husband, Khal Drogo (Jason Momoa) and her baby.

3. Tyrion’s Nose

In the Battle of Blackwater – which took place toward the end of Season 2 – Tyrion (Peter Dinklage) was disfigured after being attacked by a member of the King’s Guard on orders from Cersei (Lena Headey). While he has been sporting a nasty scar on his face ever since, in the books the character actually loses most of his nose as well. The show’s producers opted for a less horrific version of the fan favorite character’s injuries.

4. Arya And Tywin

In Season 2, Arya Stark ended up at Harrenhal after she was taken prisoner – and thought to be only a peasant boy. In the books she stays largely in the background as one of many servants to Roose Bolton. However, in the show she becomes the primary cupbearer to Tywin Lannister (Charles Dance), setting up more than a few tense scenes between the two characters as fans sat on the edge of their seats wondering if the Lannister leader would ever recognize the Stark girl.

5. Jaime And Cersei

One of the most controversial scenes of Season 4 was a sex scene between Cersei and Jamie (Nikolaj Coster-Waldau) Lannister that took place nearly on top of the dead body of their son, Joffrey (Jack Gleeson). Other than the grim setting, what shocked those watching was the fact that Jaime appeared to be forcing himself on his sister – though there are eventually signs the lust is reciprocal. There is nothing ambiguous about the scene in the books as Cersei clearly consents to the act, but it was a curious decision by the show to leave the encounter so vague.

6. Lady Stoneheart

In the books, the Brotherhood without Banners finds the body of Catelyn Stark (Michelle Fairley) after the Red Wedding and revives the dead woman. The resurrected, zombie-like reincarnation becomes known as Lady Stoneheart and seeks revenge on those responsible for killing her family. Many were disappointed when the character did not make an appearance in Season 4 of the show. There is still a chance she could debut in Season 5, but it does not seem likely

7. White Walkers

“Game of Thrones” has occasionally given viewers some revealing peeks at the terrifying White Walkers that lurk beyond the wall. In one such scene, one of the mystical bad guys takes a baby from Craster’s Keep and carries it away. Later. what appears to be the White Walker leader touches the child, transforming it into a tiny one of his kind. Though it is known that the Walkers take children in the books, it has not yet been revealed what happens to them.

8. Jojen

At the end of Season 4, Bran finally reached the Three-Eyed Raven, but not before traversing a frozen field filled with deadly wights. Jojen Reed (Thomas Brodie-Sangster) – who had been accompanying Bran since they made it across the wall – was killed while defending Bran from the creatures. Though the published books do not go too far beyond this point, Jojen survives the wight encounter in the novels and makes it to the Three-Eyed Raven.

9. Robb Stark

After the war breaks out between the Lannisters and the Starks in Season 2, Robb Stark takes a back seat in the books, with his battles and bravery told through other point-of-view characters hearing about them second hand. In the shows, the producers opted to keep the actor front and center, even showing the blossoming romance that develops between Robb and Talisa (Oona Chaplin) before the Red Wedding ended the character’s storyline for good.