Kyubey

3. Kyubey cannot understand (or properly grant) purely emotional concepts
   Kyubey is a creature of pure logic and completely lacks emotions. This means it cannot process human subjectivity.

If a girl asks, "I wish for my boyfriend to be happy" or "I wish for true love," Kyubey cannot grant "happiness" or "love" as an abstract state of mind. What it does is grant the physical cause the girl imagines (for example, healing Kyousuke's arm so Sayaka believes he will be happy).

If the wish cannot be translated into a physical, logical, or biologically alterable fact in the material world, Kyubey cannot properly shape it.

4. Directly altering the past without altering the present
   Kyubey does not have the innate power to travel through time or alter the timeline at will. When Homura wished, "I want to relive my encounter with Kaname-san," the wish granted her the magical ability to manipulate time through her own Soul Gem, but Kyubey himself cannot simply press a button and rewrite the past out of thin air.

In short:
Kyubey is neither a god nor a genie with infinite magic. He is a conduit of energy. His limitations are the mathematics of karma, the laws of thermodynamics, and his own inability to understand human emotions. If you attempt to ask for something that violates the logic of his energy collection or exceeds your karmic "budget," the contract is simply impossible.

1. Wishes that Exceed the Girl's "Karmic Potential"
   This is the most important technical limitation. The power of the wish Kyubey can grant doesn't come from his own magic, but from the girl's destiny and karmic significance in the universe.

Potential is measured by the impact that person will have on history (whether she's a queen, the mother of a savior, or the center of multiple timelines like Madoka).

If an ordinary girl, without any special karmic weight, were to ask Kyubey, "I want to become the creator god of a new universe," Kyubey wouldn't be able to grant it. The wish would simply fail, or the energy would instantly consume the girl because she doesn't have enough "thread of destiny" to pay for that level of miracle.

2. Wishes that Negate Energy Collection (The System Paradox)
   Kyubey's sole purpose in granting wishes is to create magical girls who will eventually become witches (or specters in the new world) and thus collect the energy generated by their transformation to combat the entropy of the universe. Therefore:
   A girl could not wish for: "I wish that Incubators cease to exist forever" or "I wish that the universe is magically saved from entropy without the need for sacrifices."

If a wish directly threatens the core directive of her race or creates a mathematical paradox that destroys its method of collection, Kyubey would simply refuse to make the contract, or the system would collapse.

Despite appearing and sounding somewhat human, Kyubey is an Incubator and has no personal understanding of human emotion. Despite appearing as an individual, Kyubey and the rest of the Incubators do not seem to have a distinct sense of self. On the occasions where a Kyubey is killed, another will step out and continue to converse as if nothing had occurred.The Incubators are an emotionless race, but seek to exploit the thermodynamics-violating emotions of the human race to produce energy

Kyubey is a creature who makes contracts with young girls to turn them into "magical girls" so that they can fight witches. In this process, the girl makes a wish and Kyubey grants it, but in return, the girl's soul is put in a small gem, which is also the source of their magic. If destroyed, the magic will disappear and the girl will die. If it is corrupted with darkness from grief, the gem will turn into a grief seed and the girl will turn into a witch. This is the ultimate fate of all Magical girls.

Kyubey is a small, cat-like creature. It has white fur and four ears, one pair representing the average cat and the other similar to those of a rabbit's. It has red eyes and golden rings around its long ears. At the bottom of the ears, it appears that it is separated into three, along with a pink-white fade and three red ovals.

Kyubey is the one who gives birth to Soul Gems and Magical Girls. Once a girl makes a contract with Kyubey, the Soul Gem will be summoned.

Kyubey can use telepathy to contact Magical Girls or girls Kyubey sees potential in.

The teadrop-like on Kyubey's back is actually a hole that they can open with it to eat Grief Seeds to prevent the hatch of Witches.

Kyubey can cause pain to Magical Girls simply by touching their Soul Gems. Once Kyubey is killed, a replacement by

another Incubator of type will occur.

Kyubey can teleport.

Kyubey is shown to be capable of showing other Magical Girls the past of a Magical Girl or even the world's history.

Kyubey also has a large memory that allows him to keep records of the last time any Magical Girl ever defeated a Witch or even a Familiar.

Homura dislikes Kyubey to no end. No matter the timeline, she will always attempt to kill him and prevent Kyubey to form contacts with Madoka and to a lesser degree with Sayaka. Kyubey usually comes to Homura whenever there is something new he has discovered or wants to talk to someone aside of Madoka.Kyubey does not usually explain in much detail what it is like to be a magical girl or how it works, she only manipulates the girls by telling them only the compromising part of the wish in exchange for becoming magical girls, He never tells the bad part as their destiny or even tells them that the soul gem is literally their souls.