Legault can be recruited by having the main lord, who is either Eliwood or Hector depending on the mode, or Lyn speak with him. His goal before joining the player is to loot all of the items in the treasure chests in that level and make off with them. He makes a clear dash across the battlefield and can be easily intercepted; he will keep anything he has already looted, so they can be used later.
Legault had been a member of the Black Fang organization since its inception. He is said to be second in ability to none except the Four Fangs, implying he had earned himself quite a reputation while he was still a member.
Through support conversations with Matthew, his past is slowly revealed as well as his motivation for leaving the Black Fang. According to him, Legault was able to join the Black Fang because of his nimble agility. He was already known as the Hurricane at the time, and was tasked with "cleaning house", which involved assassinating anyone who betrayed the Black Fang.
Legault admits that his job made him unpopular, though it was not until Sonia's arrival when he began to really consider leaving the organization after noticing that the Black Fang was beginning to crumble from the inside. Along with this, his duty as the cleaner was changed from killing only traitors into targeting anyone who was wounded and could no longer fight competently. The last straw came when he was forced to kill Aesha, a fellow assassin who had received a crippling injury that cut her career short. He appears to deeply regret killing her, and his decision to abandon the organization solidified at that point.
At this point, he appears near the Dragon's Gate on Valor, The Dread Isle with the purpose of plundering the treasure and then escaping. However, he is intercepted by one of the Lords of Lycia, who convince him to join their side and help them with his knowledge of the Black Fang. Subsequently, when the army travels to Bern, he makes another appearance in Chapter 23, where he offers advice to the three lords as they discuss their proceedings, to which Eliwood thanks him. He is seen even if the player did not recruit him in the chapter that he initially appears in.
During his stay in the Lycian army, Legault can form a tentative friendship with the like-minded deserter Heath, who Legault alternately teases or compliments for his honest and ethical nature while they brood over their predicaments. They seem to agree to travel together once the conflict is over, which Legault describes as "friendship between fugitives." Otherwise, he can share parts of his past with the Ostian spy Matthew, or strike up an ill-fated romance with the Paladin Isadora, who he meets again as an enemy a decade after their paths diverge.
With the former Black Fang member, Jaffar, Legault seems to view him with a mixture of unease and perplexity, once remarking that Jaffar's title as the unfeeling "Angel of Death" suits him. It is only after he realizes that Jaffar has warmed up to Nino, that he acknowledges the assassin has changed enormously and addresses him by his real name instead.
Legault shares a familial relationship with Nino herself as they appear to have been acquainted during his time in the Black Fang. Ultimately though, Legault cuts all his ties with her, firmly refusing her request to accompany him after the journey ends by telling her that the life he will lead is not meant for someone like her, and that she would only slow him down.
Evidently, Legault has friendly relations with several of the higher members of the Fang. When engaging Lloyd or Linus at the Shrine of Seals in Chapter 27: Cog of Destiny, he will have a short conversation with either of the Reed brothers, where he tries to convince them to lay down their arms, though this does not dissuade them from attacking him. Also, if brought on the last level and if he engages Lloyd, Linus, Uhai, and Brendan Reed, Legault will speak to each of them before any blows are struck to which the morphs will not respond.
After the war ends, Legault's fate is unknown. He could have fought in the War on Bern, although there is the possibility that he was killed later by Black Fang bounty hunters or simply went into hiding. His normal ending states that Legault traveled about the land looking for other refugees of the Black Fang to ease the pain of his own losses. His ending with Isadora, however, implies that he finds himself under Bern's employ.