Crais was not born into Peacekeeper life, but taken from his home as a child, along with his brother, to be trained as a Peacekeeper. Though it was a great honour, the pair had to fight hard to ascend the ranks, and through this time, Crais held a promise to his father that he would look after his brother. By the time Crichton arrives, Crais has become Captain, and so Crichton's collision with Crais's brother, and the resulting loss of life is enough to send Crais on a mad hunt across the uncharted territories in pursuit of Crichton.

Opportunities for revenge arise in two episodes, That Old Black Magic and Nerve, but by the time we reach the latter of the two, it is Scorpius who is firmly in charge, and Crais is powerless. This is a life changing moment for Crais, as his power is gradually overthrown by Scorpius, he finds himself in need of new allies, and seeks asylum aboard Moya. From here he makes a magnificent leap to a new command, that of newly born Leviathan, Talyn. In the episode Mind The Baby, Crais accepts Talyn's offer of becoming Captain, with a neural link to bind the two, and together, they depart.

The pair's visits back to Moya are not frequent after this, though the crew get to monitor their progress in Out Of Their Minds, where they see that Talyn defended himself against a Halosian ship, and also in The Ugly Truth where Crais's attempt to negotiate for a less destructive weapon aboard Talyn results in the loss of a Plokavian ship, and the trial of Moya's crew. After that though, Talyn becomes immensely helpful, providing the weapons power to destroy the shadow depository in Plan B, and also attempting to take out Scorpius in Season Of Death.

Crais and Talyn continue to play a large part in season 3, when Moya assists Talyn with repairs for damage inflicted by a Peacekeeper retrieval squad. A swift escape shortly afterwards strands Crichton, Aeryn, Stark and Rygel aboard Talyn. The adventures continue, and Crais witnesses Aeryn's emotional trouble, particularly after the loss of Crichton, something Crais finds difficult as he secretly loves Aeryn Sun. Showing a little of his inner strength, Crais never acts on this, other than asking Aeryn if she would like to join Talyn's crew on a permanent basis.

Whilst at first, the offer of joining as crewmates may seem sinister, nothing really comes of it, especially as Crais is in fact struggling with control of Talyn due to severe bleedback caused whenever the two disagree completely. Talyn's troubles increase towards the end of the season, and Crais finds himself seeking help from the Peacekeepers during the final episodes of Season 3 (which is when Crichton goes to the command carrier to deal in wormholes with Scorpius). Things backfire though, and it looks as if Talyn may never be free of his Peacekeeper heritage. In the final moments of Wolf In Sheep's Clothin, Talyn and Crais sacrifice themselves to destroy the command carrier, saving their friends, Aeryn Sun and the others.