Julius Belmont is the oldest Belmont to be in action at 55 in Aria of Sorrow and 56 in Dawn of Sorrow, but age has not held him back as he is still one of the most powerful vampire hunters, being the first true Belmont to use the Vampire Killer since Richter.
Aria of Sorrow
While Soma Cruz searches the castle he comes across a mysterious man who calls himself "J", he tells Soma he was in an accident in 1999 and now suffers from amnesia and is here to recover his memories, the next time the man appears is after Soma defeats the Balrog, he says the dark power inside Soma made his memories come back, his name is Julius Belmont and he was responsible for defeating Dracula in 1999 he will help Soma but needs to his weapon the Vampire Killer and is of the find it, Julius will appear a third time bit only if the player takes the route to the true ending, this time Julius will act as a boss before the final area, after the battle a conversation will reveal that Julius did not fought Soma with all his power as the good part of his soul was enough to stop him, Soma tell Julius in case he falls to the dark side Julius most destroy him, at the end of the game Julius as well as the rest of the cast escape the castle.
Dawn of Sorrow
One year after the events of the last game Julius and Yoko Belnades go to the castle to stop Celia, they tell Soma to leave as is dangerous for him to stay but he decides to continue, the next time he appears is in the barrier room were he explains to Soma he can destroy such barrier but doing so will make him to weak to fight, the next encounter is before fighting Dario Julius explains he could not defeat Daria as he is not a Magic Seal user like Soma, the last time Julius appears is once again in the barrier room after destroying the barrier Julius tells Soma to be careful as he is to tired to continue fighting.
Harmony of Despair
In this game Julius is one of the many characters to use the Vampire Killer as such he shares many of the same abilities but the main difference is the ability to whip in 8 directions and use the same magnets Shanoa could use to reach different spots.
Julius mode as its name suggest is a special mode where the player controls Julius Belmont as the main character instead of Soma Cruz. There are some key differences in this mode, however. In Aria of Sorrow this mode can be access after the player beats the game and starts a new profile with the name "JULIUS", though there is no story in this mode as Julius will start the game with all the abilities to go anywhere in the castle. However he cannot equip/use any items nor level up. The only way to make Julius stronger is defeating all the bosses in order; this is not required but later parts of the game will be almost impossible if the player decides to go directly to them.
In Dawn of Sorrow's Julius mode the player must obtain either the Bad or True ending. This time there is a story and continues from the Bad ending where Soma becomes the new Dark Lord, like the past game Julius cannot equip or use any item, however he is able to gain levels. There is also an homage to Castlevania III as Julius can recruit Yoko Belnades as well as Alucard to help him. Yoko fights very similar to Sypha Belnades and Alucard will fight the same way he was in Symphony of The Night. Whichever character faces Soma in the end he will have a unique line to say as well as Soma's response.