Dilandau and Celena

Spoiler warning: Plot or ending details may follow.

Dilandau Albatou and Celena Schezar.

Dilandau Albatou is the result of a Fate Alteration experiment performed by the Zaibach Empire on Celena Schezar. Though they share the same body, Celena and Dilandau are different entities, and it is unclear to what extent each is conscious of the other's actions, memories, or thoughts.

Dilandau's reversion back into Celena is often triggered by the feeling of being alone. Celena was afraid of being left alone as a child, and to alleviate those anxieties, she was taken care of by Jajuka. Without any soldiers under his command, Dilandau becomes petrified to the point that it is difficult for him to continue as Dilandau. He also visibly suffers when Jajuka informs him that his Dragonslayers are dead.

Despite that he has access to at least some of her memories, Dilandau shows remarkably little awareness of Celena's existence. At Encia's grave, when Allen addresses Dilandau by his sister's name, Dilandau asks "Celena?" as if he has not heard the name before. He also does not recognize Jajuka as his caretaker, but his trust of Jajuka is likely influenced by Celena's relationship with her guardian.

It appears that Celena holds some of Dilandau's memories as well. By remembering her childhood with Allen, as well as the way he fought in battle which was witnessed by Dilandau, Celena was able to deduce that Allen was piloting the Guymelef Scherazade, and call out for her brother.

It is unknown whether Dilandau resurfaces after Celena and Allen are reunited.