From Halopedia, the Halo wiki
Prior to 2553 Yar ‘Dosaan worked with Major Kyle Stallock aboard The Lookout, the ship's mission was going from system to system trying to reestablish communication with colonies cut off by the Human-Covenant War. In 2553 they reached the system where Losing Hand was, initially thinking it barren; however, the Huragok known as Slight List convinced the crew to survey the system. They discovered the downed remains of the UNSC Dark Was the Night, a military cargo tender that had crashed one year ago on the planet after being damaged by a Covenant attack. Yar was the first to step out of the ship which set the crew and colonists on edge as they were unaware of the alliance between the two factions. Yar observed the humans and sneered at Kevin-A282, a SPARTAN-III, Major Stallock came out soon after and Yar stepped aside to let Stallock speak to the humans. After noticing that the humans were armed he asked if they had expected conflict, Kevin-A282 affirmed that they were but both agreed to put down their weapons. Stallock updated Dark Was the Night's crew on everything that had happened since their crash. The local population and the ship's crew were offered a way off the planet; some accepted while others remained.
List of appearances