Arieus is shown to be a kind and caring person with a deep sense of loyalty, great charisma, and skill in negotiation. He see the people of Hogwarts as a part of his own family. He was also shown to be a very wise and insightful. It was he who first believed that all Magical Races should show true loyalty to each other, and that a Leader must be willing to put his life on the line for his people to set an example for all others.
Arieus also seemed to hold a great sense of honor regarding his opponents and, despite any rivalry, possessed great respect for them. He is an idealist by nature and always gave people the benefit of the doubt. This was witnessed through the fact that he considered the Muggleborns allies and was willing to form an alliance despite being a Pureblood. This put him in odds with Many other Purebloods.
He also sometimes has a dark sense of humour, as shown when he was willing to hit a group of older wizard with a bat-buggy curse because he thought it would be fun, and when asked by an Auror what had happened, he stated that they were "not okay".
He even has a very jaded and emotionless approach towards the tragedies of war as a way to cope with it, to the point of light-heartedly joking about them, as seen from his cheer at having "destroyed the alliance's mind" in his game, which further demonstrates his knack for reversing the situations he finds himself in.
Beyond his more serious disposition, Arieus is something of a notorious flirt and playboy. Having an immense interest in beautiful women, he tends to charm his way into their good graces, and attempt to woo them over. Additionally, Arieus isn't above less dignified advances either, as seen in his tendency to focus on the appealing aspects of the ladies around him. Even still, He has his good points in dealing with women as well. Whenever he senses a woman may be in trouble or in need of help, he usually ends up being one of the first, if not the first in general, to come to their assistance. This goes as far as standing up for a lady who he feels may be insulted or emotionally abused.
Alongside his womanizing behavior, Arieus is something of a trouble-maker, often being one who enjoys causing mischeif among his friends and companions. As Arieus is of the exuberant sort, playing games with others, usually at their expense, is quite commonly seen. This usually involves some kind of trick, like knocking out others and assuming their role and position, or coming up with schemes to further his own goals, with a bit of playfulness added in. Usually, due to Arieus's shady habits, he often ends up easily lulling others into a false sense of security, either through taking advantage of their low intelligence, trusting natures, or manipulating their emotions, and will then show his true colors when least expected. Among some of Arieus's favorite pastimes is making backdoor deals with others, either for the fun of it, to gain some kind of profit, or even both at once. This can range from selling private information or possessions to others, to making secret plans with comrades to ensure the deal's success. This is such a a common habit of Arieus's, that his crew has often become wary of him whenever he appears to have hatched a new idea.
Coupling his love of dark dealings, Arieus has something of a fondness for gambling. This was most obvious when he expressed how he enjoyed his visit to many casino's along side his father sometime before Attending Hogwarts. Typically, when not busy with his other hobbies or activities, Arieus tends to enjoy making bets out of any competition that comes up. He once tried making a deal with a older Student that if he could best her in a fight, that she'd go out with him. Most of the time however, Arieus tends to gamble money or possessions through more traditional means, such as craps, billiards, card games, or even roulette. Given Arieus's willingness to hit below the belt at times, Arieus usually finds a way to turn even a lost bet into a victory. Though whether he gets caught doing so or not usually depends on the people he's with at the time. This habit characterizes him so well, much like his other interests, that his friends tend to consider any bets or deals with him to be "deals with the devil, but he rarely shows any hesitation in making low blows when he feels like it. All in all though, given Arieus's manipulative skills and unpredictability, people somehow end up forgetting his past transgressions and will continue making bets and deals with him, whether for their own good or not. Despite him being a Gryffindor he tends to act more like a Slytherin most times.
When caught in the middle of any act, Arieus tends to play dumb. Given his manipulative abilities, He tends to know how to get people to sympathies with him the most, depending on whom he talks to. When flirting with an 7th year witches back in his 3rd year for example, he'll usually try to compliment there on her looks to get out of any trouble that may arise.