Nile

Nile is one of the few surviving immortals from the Advenna Avis.

Chronology
Nile is an alchemist who studied alchemy with fellow immortals Denkuro and Zank Rowan at Majeedah Batutah's floating workshop (though the three of them did not become immortals until much later). Nile was named after the river where his family was born - the Nile River in Egypt.

1705 the Ironic Light Orcastra
Zank Rowan mentions that Nile wants to burn down Lotto Valentino for the usage of drugs and that it was the reason he was not sent there to speak with Dalton. Nile boarded the Advenna Avis along with his fellow alchemists. Like other passengers, he drank The Grand Panacea and gained immortality. After Szilard Quates failed to devour Sylvie Lumiere, Nile confronts him and severs Szilard's arm after cornering him with the help of Maiza and Denkuro.

2001 the Children of the Bottle
Nile joins Maiza, Czeslaw, and Sylvie in their search for Elmer. He now wears a mask, and claims he wears it so that nobody would accidentally devour him in their sleep. His real reason for wearing the mask is much more personal: after spending centuries fighting in various wars, he is distressed that he shows no sign of emotional distress on his face. He wears a mask because he cannot bear to look at himself.

When the immortals first reach the town lost in time, Nile is asleep in the trunk, and it is not until later that he is woken up, accidentally having been forgotten in the trunk by his companions. They are then saved by Phil and brought to the castle Elmer is staying at.

When Elmer greets the door to see who is their Elmer does not recognise Nile because of his mask.

Nile and the others take up temporary residence at the castle hoping to discover what secret Elmer is keeping, all the while playing his little game of cat and mouse. Eventually Nile and Maiza stumble upon the library where they discover notes on homunculi and their creation process.

Finally after cornering Elmer, they are taken to the research lab where Phil and Dez where born. They are introduced to Bild Quates, who explains what Szilard (his ancestor) attempted to do in the city all those years ago.

Nile later confronts Felt, and defeats his original body along with Maiza and Elmer, saving Sylvie in the process.

Afterwards he accompanies Felt, Phil, and his companions back to New York.

Trivia

 * Nile has fought Shizuo Heiwajima (From Durarara!!) at some point. The battle ended in Shizuo's favor.