Mullo is a small mouse-like creature with gray ears, her eyes are pink.
Like all kwamis, Mullo can fly, levitate, phase through solid objects, and carry things that are bigger than him.
Mullo can transform the holder of her Miraculous into a mouse-themed superhero by going inside their Miraculous.
Thousands of years prior to the series, Mullo and the other Kwamis traveled the universe, unable to interact with any creatures, particularly humans. This was until a mage forged the Miraculouses, so Mullo and the others could both interact with mankind and grant them the ability to transform into heroes; Mullo and the Mouse Miraculous able to give a person the ability to grant other people superpowers.