Aiber is a professional con-man who "sometimes helps L do his dirty work."
Aiber is a tall man with slicked back, shoulder-length blond hair and light blue eyes. He has chiseled facial features with high cheekbones and a prominent jaw. He dresses professionally, usually in a suit and black coat.
Aiber is a professional con-man who possesses the special ability to blend in with various types of social groups. Aiber once mentions that the evidence L has on him could land him a lifelong sentence in prison and that L saved his life on a couple of occasions.
Death Note 13: How to Read states that he speaks "numerous languages and often assumes false identities" and that he gets the biggest thrills from swindling and living "life on the edge." Having these abilities and his "good looks," he is able to build trust with certain individuals and extract information from them.
Aiber plays the role of Eraldo Coil, one of L's detective aliases, during the investigation of the Yotsuba Group. Aiber uses his initial "A," just like L, when communicating through computers. Aiber dislikes guns and the idea of using them, but when the Task Force chases Kyosuke Higuchi after he flees Sakura TV, he reluctantly fires a shot at Higuchi's head (and misses).
After L's death, Light Yagami writes Aiber's real name in his Death Note. In the manga, Aiber dies of liver cancer in a hospital in Paris, France, with his family at his bedside. In the anime, Aiber presumably dies of a heart attack or of alcohol poisoning in front of his son and wife.
According to Obata, his editor told him that Aiber was a "sarcastic, comic relief" character. Obata said that he wishes that he could have drawn Aiber to be "more comedic." Obata believes that if he drew Aiber and Wedy to look "a little bit more original," Ohba could have included the characters in a larger role in Death Note.
- The given name Thierry (ティエリ, Tieri) is a common French male given name.
- The surname Morrello is Italian, so he may be of Italian descent. It is also the name of an Italian mafia family in New York, a reference to Aiber's criminal profession.
- Tierry/Thierry (ティエリ, Tieri) is also similar to the romaji for 'cherry' (チェリー, cherii). His name is a pun on the morello cherry.
- It is suggested that he is French, or at least resides in France since his given name is a French name. He dies in France with his family, and he is shown staying near the famous landmark known as the Arc de Triomphe in Paris during his call to the Yotsuba Group.
- It is implied that, along with Wedy, Aiber briefly worked under L during the Los Angeles BB Serial Murder Cases.