After the fall of Crimea, Bastian seeks refuge underground, in hopes of liberating his country from Daein. After joining up with the Crimean Liberation Army, he finds his ideologies conflicting with Ike's authority, most likely stemming from his lack of pedigree. Bastian eventually warms up to Ike after witnessing Elincia vouching for him, alongside Ike's proficiency as a hired guard. After the events of the game, he will hire Volke to perform certain "jobs", some of which are connected to particular events in Radiant Dawn. One of these jobs involve the capture of Izuka in order to find a cure for Renning's crazed stupor, an ailment inflicted upon him by the Feral Drug.
In this game, Bastian serves as Crimea's Deputy Prime Minister and one of Queen Elincia's most trusted advisors. He is, however, noticeably absent from court during the Ludveck crisis, and is instead sent to Daein by Elincia as part of a diplomatic mission to determine the abilities of the newly-crowned King Pelleas. Despite his absence from court, Bastian still plays a significant role in saving Lucia, as he hires Ike and the Greil Mercenaries to halt Ludveck's troops laying siege to Castle Crimea.
Bastian's close contact with the assassin Volke ultimately leads to the eventual capture and execution of the fugitive Izuka.