WISHGRANTING
The main ability, and in fact life purpose, of lepitsunes is to grant wishes to as many living creatures as they can. This power is innate to them and comes from the stardust that makes up their bodies. Rather than sudden acts of magic where they conjure objects or realities out of thin air, lepitsunes primarily grant wishes by giving the wisher a boost of motivation or luck in order to achieve their goal. One could say their magic is more so in the form of vibes and energy where they manifest the achievement into happening. For example, someone wishing for a friend may gain a boost of social confidence from a lepitsune, or the lepi's assitance in orchestrating an event where friendship is likely to happen, such as finding a lost object or guiding over someone with common interests. Another lepitsune may simply take it upon themself to be that person's friend instead. Each lepitsune's personal approach and interpretation of a wish is different so there is no right or wrong method in fulfilling it - the wish is considered granted when the human acknowledges that it is.
Lepitsunes enter into a wish pact with someone by resolving to grant a wish for them, and as they draw power from their stardust, they generate heat and gain an energy halo while wish granting is in progress- the more experienced the lepitsune, the larger and brighter the halo, and the faster and more effective the energy manifestation is. The sign of an exceptional lepitsune is a permanent halo above its head, and this may be brought about either from honed skill and power, or in rare cases, from birth.
CORRUPTION
For more healing-based, materialistic or otherwise impossible wishes, lepitsunes have a small reserve of true magical power that can be used to grant them, but this must be used sparingly or it will weaken and even hurt the lepitsune if overused. This is the main culprit for lepitsune corruption - lepitsunes who feel an intense desperation or emotion to fulfill a wish for someone may overexert themselves in attempting to do so, exhausting themselves as they spend more power than they can afford.
This behavior is usually spurred on by a strong attachment for something or someone to the point the lepitsune will turn to self-sacrifice. For example, a lepitsune may refuse to accept that curing someone of a terminal disease is impossible, and will burn through their stardust in their efforts to heal them. This destabilises the stardust and makes it prone to corruption - a condition caused by infections from dark matter and negativity in the atmosphere. As a result, corruption can also be brought upon by intense negative emotion, such as a lepitsune's own anger or grief as it begins to take over their waking thoughts, or if subject to harsh mistreatment by others.
A corrupted lepitsune's halo will start forming irreversible cracks and begin to crumble, and depending on the severity of their condition they may begin to develop unsettling traits such as third eyes, rotting skin or extra limbs. However, with sufficient support, friendship and time, they can eventually recover through exposure to healthy stardust, though they remain susceptible to relapsing if not careful. If a corrupted lepitsune is left alone, however, they will spiral both physically and mentally as their stardust continues to destabilise and corrupt and may develop increasingly abnormal mutations until even their consciousness is consumed by the corruption.
Shapeshifting
Over time, myths and legends sprang forth as they do and sightings increased in number of these strange starlit creatures. People began depicting and describing them more and more based on what was familiar to them- a combination of a moth and a fox. Based on that collective consciousness, the stardust responded by beginning to conform more closely to that idea in taking the shape of the modern lepitsunes, and eventually took the moth-winged foxlike form they have today.
As generations went by they relied on shapeshifting less and less and so in most modern lepitsunes, the power lies dormant. However, the ability is still there, and can be achieved by experienced lepis, unlocked with a strong enough wish from someone for them to turn into another form. It can't be an offhanded or casual request, but must be wished for with powerful emotion and conviction behind it, such as a lonely person pouring their heart out in their longing for a friend, or someone in difficult times wishing for someone to be there for them.
Technically, they can be wished into any living form, but the most common request is for a human form by those who simply wish for a friend Shifting depends on the amount of power and stardust a lepitsune has, and they require sufficient experience and ability to hold the shifted form. Lepitsunes not strong or experienced enough can only manifest a faint ghostly form that can barely hold itself together.
The lepitsune will at first be unfamiliar and clumsy with whatever new form it may take, and lose its form easily, reverting back without warning to its regular lepitsune form, and have difficulty concealing its large fluffy ears and its tail. Eventually with enough practice they improve and can spend increasingly long periods in that form.