Lear'Kaus was born onboard the Mercant, a fair-sized turian vessel acquired (and repurposed) by Yenn'Tra vas Mercant. His parents were Var'Kaus vas Mercant nar Therum and Beina'Kaus vas Mercant, a Marine and an Engineer.
While doing his part for the Migrant Fleet, Lear had a desire to learn more about the universe around him. His parents were usually supportive of his decision, but he was also pushed between them, as Var'Kaus wished for him to be a Marine, fighting for the future of the quarians, while Beina'Kaus wanted him to be an Engineer, helping to assure the continued survival of the Migrant Fleet. This continued until he left for Pilgrimage, acquiring a small shuttle to do so with, and making his way to the Citadel.
While on the Citadel, Lear ran into fellow quarian Alar'Xan nar Hybrid, who was also on her pilgrimage. The difference, however, is that while Lear had just started, Alar had been on hers for over a month. Together, the duo managed to find a Pilgrimage gift with the help of Flint Locke (Real name Caecillius Corvinus), but were quickly betrayed by the turian, leading to Alar's death.
Lear soon presented his findings to the Captain of the Hybrid, Trea'Sava vas Hybrid, who welcomed the young man with open arms. Lear, however, didn't properly understand, and quickly left in an attempt to find something better (Something he would also later be mocked for, as it was a fairly stupid mistake to make). After returning to the Citadel, Lear heard about CDN, but thought nothing of it. It wasn't until his curiosity got the better of him that he joined under the alias of "Hybrid" with a forum post wondering how many species used CDN itself.
Retaking Rannoch and the Reaper War
During the recall, Lear returned to the Hybrid, quickly taking the mantle of chief engineer. Everything went fine until the Battle for Haestrom, an engine malfunction after exiting the relay resulted in overheating. The problem was quickly fixed, but later on into the battle, the problem returned, shutting down the engines and taking a large majority of the ship's systems (specifically the kinetic barriers and the GARDIAN systems) with it. Lear was the last one to depart the dead ship, boarding a shuttle from the Agnon.
Lear quickly became apart of the crew onboard the Agnon, but had difficulties settling in. Being a science vessel, it was usually always sterile and clean, something that neither the Mercant or the Hybrid were, being engineering vessels. His greatest accomplishment while onboard was during the first attempt at taking Rannoch (ending in absolute failure), in which he successfully prevented the Agnon spinal gun from lethally overheating and dispersing static build-up long enough for it to be safely dispersed.
After receiving a distress call from the Captain of the Kolosya, Vik'Sajee (whom Lear had befriended before Haestrom), Lear pleaded for the Agnon to assist, placing in a request to be transferred to the Kolosya as well. The operation will always give Lear two reasons to gloat: He had gotten the Kolosya running again when nobody else could, and his constant calibrations allowed the Agnon's guns to be able too fire within 2 meters of the target (something he will always be proud of, even if nobody will remember or believe it).
Lear would later help Vik'Sajee in bringing down Cerberus Agents Grizzly and Lupus , assisting mostly in getting Vik inside, but also assisting Titus Scapula in bringing down Agent Grizzly. Near the end of the operation, Lear managed to avenge the death of Alar'Xan by shooting Flint Locke point blank in the head with a Mantis, something the Turian had once told him would be the worst way to die.