Tyrus Harlaw is an unseen character in Game of Thrones. He was killed during the Greyjoy Rebellion, several years before the main story begins, and is not expected to appear in the series, though he is mentioned during the first, second, third, and sixth seasons, and is also briefly mentioned in the short story Lord of the Hunt. Tyrus doesn't appear in the books; he and his son Caspus are replacements for the character of Rodrik Harlaw, also known as "Rodrik the Reader", to avoid characters that deviate from the other Ironborn in the television series.
Tyrus Harlaw was the head of House Harlaw, a powerful vassal house of House Greyjoy, and the Lord of Ten Towers. He was also the Lord Defender of the Iron Islands during both Robert's Rebellion and the afformentioned Greyjoy Rebellion.
Tyrus was one of Balon Greyjoy's closest friends (and was also his brother-in-law) played a large and important role in the Greyjoy Rebellion, leading the Ironborn armies into battle on multiple occasions. During the Siege of Pyke, however, Tyrus would engage in a legendary duel with Garrick Grayburn, one of King Robert Baratheon's commanders, during the Siege of Pyke. The duel would ultimately result in the death of both men.