10^−43 is a witch from the game Magica Record. Its presence was known only through its familiars, the Echos, until the witch was finally revealed in the first chapter of Arc 2.5. In the Magica Record's anime, a greenish hue was seen inside its barrier. Its mostly thought to be the final evolution of the Echos as they grow.
When she was a magical girl,10^−43's wish was " Give me a fertile paradise for my family's prosperity."
The witches are as follows: - 10^−43, a witch aiming for ultimate prosperity by meddling in history across all eras. After disrupting the system governing Puella Magi's fate and absorbing its world-encompassing membrane, she has become a sprawling city with a Labyrinth vast enough to engulf the Earth. Now just one step away from existing across all time, she needs to absorb the power of infinity. Unable to move on her own, she must depend on her offshoots to accomplish this. -10^−1, A witch driven solely by an unyielding urge to proliferate, with no consciousness, unknown origin, and sense of age. She never considers her purpose, mindlessly following the instinct to replicate herself endlessly, aided by her previous offshoots. However, without any intent beyond proliferation, she is easily destroyed when found, no matter how many copies of her exist. -10^−3, a more developed form of a witch who endlessly proliferates, as if compelled by an inescapable duty. With rigid wings, she now glides through the skies and monitors three different eras. Despite this evolution, her core instinct remains unchanged—she exists solely to replicate herself. She instinctively tries to eliminate threats and occasionally signals warnings to her other selves, but the less mature versions cannot comprehend her messages, rendering her efforts meaningless. -10^−7, A more evolved form of a witch who relentlessly proliferates, as if bound by an unyielding duty. To ensure her parent witch's supremacy, she has decided to sacrifice herself, becoming the ultimate meal. In preparation, she has consumed and manipulated many other witches, refining herself into perfection. Now, this mature witch glides on golden wings, able to watch over seven eras, with her yin and yang essences perfectly balanced to create a dish with no distinct or overpowering flavors. The resonant sound of her trumpet is a tribute to the parent witch who gave her life.