Muses arise from one of the 7 Ideals, which flavour the Creative Juices they are made from. When a Muse is conceptualised, they are centred around one particular Ideal, though at first this will be very generic. Muses then use that Ideal as a guiding principle to literally define who they are; this will be very apparent in a Muse's younger stages. As they grow and mature, their identity becomes more complex - shaped by their experiences with other Muses and the world of Dream around them while still adhering to the principles along the axis of their Ideal. Muses feel the emotional effects of all situations that they encounter. Therefore, it is possible for Muses to have complex personalities and many different intentions for their powers, but their powers will always manifest in a manner concordant with their Ideal.

Muses are a personification of Jo’s Creative Juices - manifested from the central source of Creative Juices within Spindle, the Juice Battery. Muses may form de novo from this energy, or be formed by a combination of two or more other Muses. Newborn Muses look like human babies, though they grow rapidly to adulthood depending on how active they are in Jo’s mind. The more Jo thinks of them or uses their power, the faster they age to a fully-grown state - physically represented by looking 18 in human years. A quickly growing Muse can be fully grown within 6 months, while slower growing Muses can take up to 5 years to reach maturity. Muses can also gain non-human body parts as their concept solidifies, but this has become less common as Jo has grown older and has lost interest in cartoons and other less conventional inspiration.

Muses are energy filled beings that are built on narrative. While they cannot suffer from any physical effects of human disease or injury, they can feel the emotional effects that these processes entail. While Muses do not need to eat, drink, wash their clothes, admire art etc., it can be assumed they still do these things because of the positive mental state that comes with these activities - or at least they don't allow themselves to suffer the normal effects of not doing tem. Muses are only tangible in the context of other things within Dream. Much like Muses can sit in a chair or drive a car constructed from material in Jo's Dreamscape and atmosphere, Muses are also physical beings in context of each other. Therefore, any object manifested in Dream that is used with the intent to maim another will do so, and the victim will feel the effects of the attack. However, this does not change the level of Creative Juices a Muse contains and therefore does not contribute to Fading.

Muses may be formed when Creative Juices in the atmosphere condense into a human form de novo. However they may also be made by a combination of 2 or more parent Muses of any gender. Thus, it is possible for Muses to have parents, grandparents and siblings. Whether or not Muses live with or care about their family differs on a case-by-case basis.