During their childhood, James and Ruwan Ackerson made up a skeleton key called the Key of Osanalan which was created to rescue the "Princess" as part of their make-believe games.
When James Ackerson was held captive and interrogated by the Jiralhanae, he said that the Halo Array will not properly activate without the Key, causing the Covenant to go on a misleading search for the "Key." Ruwan, after realizing the importance of the Covenant's belief in the key, contacted the Covenant, saying that he would give them the Key when they met. Once they arrived, Ruwan then informed them that he was in fact the key. Confused, the Covenant brought Ruwan to their ship. In actuality, Ruwan was implanted with an organic tracker. Moments before Nassau Station used its MAC cannon to destroy the ship, Ruwan told the Minister of Inquisition to "kiss my ass".