Attentive: No one in their right mind would call Leona "considerate", as that word usually connotes an expectation of care being taken after consideration. But Leona does spend a considerable time, well, considering things, so it's more apt to call him attentive. Though Leona hides it under a thick layer of callousness, he is attentive to those around him he considers important. He is mindful of the strengths and weaknesses of his schoolmates, often (but not always) giving the most accurate assessments of their abilities due to the attention he pays. He shows himself to easily recognize when other students are injured and covering or compensating for those injuries, calling out Vil for doing exactly that when he was competing on Leona's team during a contact-sport festival.

During that same festival, Leona picks his teammates based on their physical skill, their ability to work well with him, and his ability to offer them something convincing enough in exchange for their participation, and due to him being so observant, each of his assessments are accurate and effective. None of the people he asks reject him, and while one team member is taken out by heatsickness, the rest perform physically exactly as Leona expects them to.

It isn't purely beneficial to just himself, either. He takes the others around his country during this event as well and is almost always the one to explain what they're seeing, calling attention to the work of artisans, detailing the history of geothermal energy in the area, and even connects the personal interests of his visitors to certain trades in the country. In other events he calls attention to the songs popularized by his country, and in his classmates dreams he is the one to correct an underclassman who doubts Cater's magical ability, to the point that he even gets annoyed when Cater starts deliberately pretending he's weaker than he is to get Leona's goat. Pointing out all of these things ultimately doesn't benefit him in the ways he usually tries to be crafty, suggesting that he isn't just attentive for the purpose of being manipulative.

Leona pays attention because he cares— it's just that his care and attention are eclipsed by all the rest of his bullshit.

Nihilistic: to say Leona is defeatist isn't quite correct. In most cases, Leona can envision, and sometimes even manifest 'victory', whatever that means for the situation. however, he often fails to see a point in victory, due to the deep depression he struggles with. "No matter how much effort you put in, nothing will ever come of it. Everything is meaningless; absolutely everything. Everything is decided from the moment you're born; give up!" This sentiment is present with him when he overblots, but it's also one he repeats often in moments of high stress. He shows strong indications that the people he works with at home, namely his brother, the Crown Prince Falena, and the government, do not take his contributions seriously nor do they accept his efforts as being enough in many ways. Some of his populous, including previous royal attendants, see Leona as a bad omen or even as evil because of his terrifying magical power.

All this, combined with Falena's carefree spirit and the fact he is beloved by their retainers and people, led Leona to internalize the idea that if he had just been born first, he wouldn't be suffering. They would see Leona's power as protective, his melancholy as carefulness, and his quietness as respect. He couldn't accept the idea that might not make a difference, nor could he accept the idea things could improve for him in the current reality. He began to lash out against others, forcing distance, since he saw no point in getting close if he could not change anyone's opinions of him. He no longer put in effort to anything, unable to bear with the disappointment that would come if he put real passion into something and still couldn't succeed.

This nihilism made him prone to pushing others away through hateful words and even violent acts. In search of freedom it drove him from his family, and it prevents him from recognizing the loyalty and love people have for him as real. But because he isn't a defeatist and sometimes does try in spite of himself, because he can't fully extinguish the light of hope inside him, he often ends up leading people toward victory, getting overwhelmed, abandoning ship, and being called out for it by others.

Manipulative: with his political power and personal freedoms limited, Leona developed a silver tongue quickly. The retainer who raised him, Kifaji (Neiji in EN), remarks that Leona is the proudest, unruliest, moodiest, and brightest prince he'd ever raised. Leona's intelligence and awareness are a blessing and a curse; he learned quickly how he needed to act to get his way, even when there were so many other ways he could never do so. He learned how to use other people's wants and needs to make them believe that fulfilling his wants and needs in the moment benefit them— or otherwise, that the outcome was unchangeable. In situations where Leona may have otherwise gotten in trouble for things, he learned to reason with people as to why he couldn't have done better, why it wasn't his fault— or why what he'd done needed to be done.

he also learned that he, in many ways, has a larger budget than many people. he can offer money, time, power, and intelligence that others can't, and if necessary will leverage them (less often money) in someone else's favor as though he doesn't benefit from what he's getting permission to do.

he sometimes uses this manipulation to hide his care for others, actively making people feel that he ignores their needs in order to maintain the unhealthy distance between himself and others. Leona makes it clear that he does not care if Ruggie steals from him, stating that anyone who can successfully steal from him deserves their spoils. Thanks to Leona's shitty attitude, no one can really say that Ruggie is wrong for often being mad at Leona, or even for tricking him to get more money or stuff out of him in exchange for his services. This is all according to design for Leona. As long as he's the worlds' worst boss, no one can get mad about how things work between them, but he's also not acting as charity. he does this with others as well, often finding 'sinister' or selfish reasons to help people with things... when ultimately, his so-called selfish motivations don't change the help he actively gave someone.

it can even be said that he manipulates himself. Leona is so desperate to stick to his unhealthy mindset, and takes a long time in the story to let go for the sake of development. He explains others kindness away when he can, and doesn't easily let himself accept the loyalty and love others have for him as real. It's something he's begun to work on for himself, but there's no chance working on that will make him less manipulative toward others.

all in all, when victory is achievable in a situation, Leona will do anything he can to win, including using underhanded and manipulative methods.

Self-sabotaging: At school a predominant part of Leona's problem is that he has already completed more than NRC's curriculum and as such is never learning anything new at school. Being so overly trained can tank motivation, as the target isn't being challenged to grow in any way. Leona's fallen victim to this; bored by every single class and ultimately never benefiting from school, he doesn't see much point in going to class at all, let alone participating in it. he speaks despairingly of his own efforts and when confronting his darkness alone, it's acknowledge that Leona would rather not put a real effort into anything for fear of that effort never being enough and the associate rejection that comes with it.

it's a deliberate move; he is simultaneously rejecting work, rejecting failure, succumbing to futility, and also cultivating a standoffish image. If he prevents others from getting closer, then he never has to be upset when they turn their backs on him. If he doesn't contribute effort at all, he doesn't have to be upset over effort wasted. If he acts the part of the villain before anyone else can put him there, he doesn't have to be villainized on anyone else's terms.

because he's been so stripped of his autonomy in being able to determine what he can be, he exerts that autonomy in deciding what he can't. and even when he does put a sincere effort in, when Leona becomes overwhelmed, he doesn't ask for help or find solutions. he just Stops. he stops showing care, he stops completing tasks, and he stops reasoning. Even in a dream scenario where he was made to be king, Leona put up a strong effort at first, got overwhelmed, and when he couldn't emotionally handle that overwhelm, started pushing everyone away and doing nothing but eating, sleeping, and lamenting.

but no one had conspired to end Leona's success in that dream; he'd simply run out of solutions on his own, become overwhelmed and burned out trying to meet everyone's needs. If he had relied on the people around him, he may have avoided his 'unhappy ending'. but just like outside of the dream, once Leona could no longer imagine himself winning, he stopped playing the game altogether. He became bitter, resentful, lashed out at everyone who was close to them until they couldn't bear to stay around him anymore. The dream was all an exaggeration of what he does outside of dreaming, but it strongly illustrates the attempts he makes in real life to ruin his own plans.

other people don't even have to put that much effort in to stop him. Leona accepts defeat far too easily once he's decided the effort isn't enough, and gives up before anyone else needs bother. ultimately he wasn't overthrown as king in his dream as much as he actively ran away from the dream entirely. he believes people will turn their backs on him anyway, so there's no point in letting them get close.

Lion Beastman: so basically he's a humanoid being descended from animals. he has certain animalistic traits, namely in having a lion's tail and ears and:

Sense of Smell: Leona sits squarely between Jack (better) and Ruggie (somewhat less strong) in terms of his ability to pick up scents stronger than a human could. Almost all beastmen seem to have better senses of smell than humans, but Jack establishes that beastmen can't smell as well as their animal ancestors. Where Jack seems to be able to follow scents and track them to some degree but not to identify them, Leona in comparison doesn't seem to track by scent but is capable of identifying certain kinds of magic by scent, as well as being able to identify when someone doesn't have magic. He also mentions being able to identify what people's species are, not just in being able to identify overarching races (human, beastman, direbeast, fae, merfolk) but in the case of non-humans their specific subsets (hyena beastman, dragon fae, octopus vs eel etc.) This was likely deliberately trained into him as the other beastmen present do not mention it.

with regards to magic it seems Leona's sniffing can identify a certain degree of spells around him (the way other mages of his caliber would use survey spells). he also routinely demonstrates that he has a great measure of the other students' magical capacities, suggesting that he can identify that some are stronger than others.

I would be making the magic-sensing an opt-in ability and/or asking permission before having him ID magic on others.

Sensitive Hearing: it's not entirely clear how sensitive, but like most beastmen he can hear better than humans. he can hear whispers pretty easily even when not right next to the whisperer, can hear loud noises from further away than others, and tends to be playing dumb if he pretends not to hear someone muttering, but it doesn't seem like he can hear three doors down or anything like that. he does tend to complain if sounds are sharp, repetitive, or loud. he doesn't make any mention of being able to identify magic by pitch while Ruggie is able to discern the weight of coins by their sound, so it's safe to assume Leona just has average hearing abilities for a beastman and isn't particularly exceptional about it.

Magical Skill: Leona is a well-trained mage who has operated at the skill of a professional adult since before his enrollment in Night Raven College, making him effectively the most educated and skilled non-fae student in the cast. It is stated that his magical reserves are "enormous" and that his launch speed is "sky high". he might not be able to perform specialties that are unique, but has a general mastery of magic and excels in his own specialty. the in-universe general mastery of magic includes being able to change his own clothes and that of others', command inanimate objects to move and bend as though animated, change the colors and other cosmetic qualities of objects, bless/curse objects, remove stains using magic, and other 'cantrip' style spells.

shapeshifting magic is restricted by law and Leona does not have legal clearance to practice it, and otherwise implies he is incapable.

he is not capable of reproducing other Unique Magic/Signature Spells.

he is not omnipotent, not impervious to having his power limited by outside technology or spells, and does not have a near-limitless capacity like Malleus.

he seems to lose strength deeply after using a lot of magic, and mentions being tired and needing to sit down to rest and recover after these large expenditures of energy.

while he does seem to be one of the strongest non-fae students, he is still susceptible to and damaged by blot, unlike Idia Shroud— another way that 'power levels' aren't necessarily the end-all-be-all to a mage's abilities and one of the biggest reasons why so-called "weaker" mages were able to defeat Leona during overblot.

Unique Magic/Signature Spell: KING'S ROAR. A wide Area-of-Effect spell dries out any object, organic or otherwise, and turns it to sand. Leona himself describes it as difficult to control to the point he won't use it in tight spaces for the risk of turning unintended targets to sand. It can still be targeted to a single object in a more open space, but the risk is just apparently too high when things are too close together. it is a potentially fatal spell, and unrestricted, it can affect a large swath of land, parching the earth and scorching trees dry. I imagine that if he COULD do this in game it would be like. way less big, but also good with limiting it altogether.

Blot/Overblot: using magic in Leona's world causes a type of negative exhaust that may taint their souls. if a mage is in poor mental health condition and continues to use magic without resting to undo the accumulation of blot, their soul may overflow with blot and a phantom may emerge to attempt to possess their body as a vessel. when that vessel is fully spent, the remaining husk fully becomes a magic. this operates as a kind of magical fatigue system, and Leona has experienced overblotting once in the past. it is one of the many ways in which Leona isn't all-powerful, as he is also well-trained enough to theoretically manage his blot well despite his immense power. personally I don't care about if he gets to be able to overblot, I just like using blot build up as an excuse to not let him use too much offensive magic.