Yull was an Unggoy stationed aboard the Rapid Conversion and was part of Dadab's group. He was the first true Covenant casualty of the Human-Covenant war (excluding two Jackals who were killed in a pre-Battle of Harvest confrontation). He killed Osmo by jumping on him, biting and clawing at him, ripping his stomach apart. He was then killed by Tartarus, who pulled off his mask and threw him into a whirlpool and down a series of waterfalls because he threatened the Jiralhanae's plans. He died of suffocation on February 11, 2525.