When trying to come up with synonyms for the phrase "most niveous," a few different options come to mind. "Most snowy" might be a good choice, as it connotes a sense of whiteness and winter magic. "Most icy" could also work, indicating a sense of cold or slickness. "Most pristine" or "most pure" might be synonyms to consider as well, emphasizing a sense of cleanness or clarity. "Most milky" might also be an option, although this could suggest a different texture or consistency. Ultimately, the best synonym for "most niveous" will depend on the context and desired tone of the text.