Dio is 16 years old and is a member of the Guild (brother of Delphine) He is very eccentric and takes an interest in Claus because of his flying abilities. His bodyguard and best friend is Lucciola. Dio is VERY skilled at flying.

Throughout the series Dio follows Claus, or "immelman" as he calls him. He is first introduced when Guild forces attack the Silvana to capture Alvis. He begins to play with Claus, having the opportunity to shoot him down twice but spares him.

At the Horizon Cave 8 Dio and Lucciola participate so that they can race against Claus while Delphine is at the Black Market Auction.

Dio loses to Claus which at first makes him angry, but furthers interests him in Claus. He actually makes a bet with Claus that if he (Dio) wins, Claus can tell him his real name. (yeah, that’s Dio for you.) On his way out of the cave, him and Lucciola see Claus and Lavie stranded and they give them a lift to the Silvana where Dio and Lucciola end up staying for quite some time.

We begin to learn that Dio is running from his sister so that he doesn't have to be part of the Right of the Covenant. Dio ends up finding happiness aboard the Silvana and is actually given a birthday party by the crew. While on the Silvana, he gives Alex his houses mysterian to gain his trust.

However, Dio's world comes crashing to an end when Delphine comes after him and takes him back to the Guild where he changed...he loses his freedom and personality and becomes a mindless zombie. Delphine forces him to take part in the Right of the Covenant. He wins and becomes next in line for the title of Maestro.

Lucciola sacrifices himself and helps Dio escape with Claus and Alvis. The three crash and are taken to a hospital where Claus and Alvis leave Dio. Dio eventually wakes up and begins to relive his memories and chases Claus and Lavie into the grand stream. His final moments are him thinking he's racing Claus again in the Horizon Cave 8. He remembers telling Lucciola to jump out so his ship can go faster. Dio thinks he wins when he crashes into a flock of rainbirds thinking it's the finish line. However, he sees Lucciola is missing and thinks Lucciola really jumped out (lucciola was never there to begin with...remember, he's reliving his memories) His ship is knocked back by the winds of the grand stream he presumably falls to his death...or does he?

>Copied from Episode Guide 26 "Resign"<

-Dio’s Death: This is debated quite a bit. Some people think when his ship was knocked over and he went flying that he died. However, there is some art in the final DVD that shows a picture of everyone looking surprised to see someone. You then see a hand waving and the person is dressed in a guild uniform.

Another piece of evidence that could suggest Dio is alive is the way Mullin was suggested as dead. We see Dunya going into the Claudia unit and seeing Mullin hunched over like he is dead. We then see Dunya running out and crying. However, at the end of the last episode Mullin is alive and has kids with Dunya. Because of this, it is very much possible Dio is actually alive.

The picture I described above can be found here or below