Concept Art: Muse (Patreon)

The Muse went through several iterations until it was finalized.

Here you can see the general development of the creature, starting with a fully formed face and progressively losing features until it was settled on the rightmost design.  We went with the right  because a Muse can adopt any appearance that suits its host, meaning a more vague baseline would cement the idea that a Muse has no inherent look, that they are reliant for others for their appearance.