The term "dark ash-phase" can refer to a variety of different color shades and hues. Synonyms for this term might include "charcoal," "slate," "ebony," "jet black," "midnight," or "smoky." These words convey a sense of darkness and depth that can be used to describe a multitude of objects or occurrences, from the color of a stormy sky to the hue of a piece of wood or stone. Depending on the context, you might use one synonym over another to accurately describe the specific shade of "dark ash" you are trying to convey.