After Lucerys Velaryon was killed by Aemond Targaryen, Lucerys's stepfather Daemon Targaryen hired two assassinates to kill Aegon's and Helaena's children, Blood and Cheese. Blood was a former Goldcloak and Cheese was a rat-catcher who knew all the sewers around King's Landing. This meant that they both had perfect recognition of the layout of the Red Keep. After breaking into the royal apartments, they found Helaena putting her children to bed. They demanded a son for a son. Helaena pleaded that kill her instead, but they refused. She named her younger son Maelor as the victim. However, Cheese just told Maelor that his mother wanted him dead, and some believe that Helaena named Maelor because Jaehaerys was heir to the Iron Throne, or because Maelor was just to young to understand. This request became an act of defiance against the Greens, as Blood just beheaded Jaehaerys with a single blow. By the time the guards had came, the Queen was cradling her son's body. Jaehaerys' death would eventually led to his mother's insanity and suicide.
In the books Edit
After the death of Prince Lucerys Velaryon, Cheese, along with Blood was employed by Mysaria, Prince Daemon Targaryen's spymaster, to slay one of Aegon II Targaryen' sons.
Using a forgotten passageway in the Red Keep, Cheese led Blood into the heart of the castle unseen by any guard. The two men crept up through the walls and slipped into Queen Alicent Hightower's chambers. Once inside Cheese bound and gagged the Dowager Queen whilst Blood strangled her bedmaid. Then they waited for Queen Helaena Targaryen and her children to arrive.
Once Blood and Cheese confronted Helaena in the Tower of the Hand they told her to name which son she wanted them to kill. Helaena offered herself but they refused, stating it had to be a son. Although Helaena eventually named her youngest son Maelor (after Cheese threatened her that Blood would rape her daughter Jaehaera if she did not choose one), they killed Jaehaerys instead. It was Blood who slew Jaehaerys, striking the boy's head off with a single blow. After killing the prince Blood and Cheese did no further harm to Helaena or her surviving children and fled with the prince's head in hand.