Jasper Wylde, called Ironrod by the smallfolk, was the Lord of the Rain House and the head of House Wylde during the reigns of kings Viserys I Targaryen and Aegon II Targaryen. He served as master of laws for both kings.
In the television adaptation House of the Dragon, Jasper is portrayed by Paul Kennedy.
According to Eustace, Lord Jasper's sobriquet Ironrod derived from his unbending attitudes to matters of law. Mushroom, however, claims it was from the stiffness of Jasper's member, as he sired twenty-nine children on four wives before the last died of exhaustion.
When King Viserys I Targaryen died in his sleep in 129 AC, Lord Jasper was called to the small council convened in the chambers of Queen Alicent Hightower. Plans were made to crown Alicent's son as Aegon II, instead of Princess Rhaenyra, who had been named Viserys's heir. With Lord Lyman Beesbury the only member of the council in support of Rhaenyra, Jasper reminded him of the Great Council of 101 AC, and the Old King Jaehaerys I in choosing Prince Baelon as his heir over Princess Rhaenys in 92 AC. Jasper also discussed Aegon the Conqueror and his sister-wives Visenya and Rhaenys, and the Andal tradition wherein the rights of a trueborn son come before a daughter. When Grand Maester Orwyle questioned asked about those not willing to bend the knee to Aegon II, Ironrod responded they would die as traitors.
As the Dance of the Dragons progressed, Jasper advised that Prince Aemond Targaryen should summon Lord Ormund Hightower and Prince Daeron Targaryen from the Reach. Aemond, however, disregarded Jasper's caution and instead headed for Harrenhal.
Jasper was taken captive by Rhaenyra during the fall of King's Landing in 130 AC. Rhaenyra had several nobles executed for treason, with Jasper being beheaded after Ser Otto Hightower. Ironrod insisted to his death that the Iron Throne goes to a king's son before a daughter.