“We must, however, acknowledge, as it seems to me, that man with all his noble qualities… still bears in his bodily frame the indelible stamp of his lowly origin.”

The Descent of Man (Charles Darwin)

Muses arise from one of the 7 Ideals, which flavour the Creative Juices they are made from. When a Muse is conceptualised, the Ideal that they are made from is chosen based on the real world influence for that Muse, be it a character, person or experience in Jo's life. Muses then use that Ideal as a guiding principle to define who they are. As Muses 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. However, they can grow to fall anywhere along this axis. Muses feel the emotional effects of all situations 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 the Ideal flavoured Creative Juices they are made of.

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 as Jo is human. 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). Ageing beyond this point is then highly dependent on Muse's personality. For example, older looking Muses tend to be wiser, mellow and hardened as compared to the more boisterous and impulsive physically-youthful Muses. 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 the Dreamscape of Jo’s mind, Muses are also physical beings in context of each other. Therefore, any object manifested in Dream that has intent to maim another will do so. However, this does not directly change the level of Creative Juices a Muse contains.

Conception of a Muse occurs when two or more Muses with sufficient Creative Juices both devote some amount of their Juice to inspiring a new Muse. This process can happen between any number of Muses, but given that the resulting new Muse will be an amalgamation of personality from all contributing Muses, the more Muses contributing Juice to make a new Muse, the more unstable that new Muse will be. Each contributing Muse is rendered weaker in the process of conceptualising a new Muse, and so each parent Muse must have enough Juice to afford to give away at least half of it in forming a new Muse. If they aren’t strong enough, it is possible for parent Muses to Fade away in conceptualising a new Muse. During this process, contributing Muses combine into one entity, which forms a bubble within which a new Muse is conceptualised. Once the new Muse reaches gestation, the bubble pops. The energy released by popping this bubble then reforms the parenting Muses.