The word "most stellary" is quite uncommon and may be difficult to come up with many synonyms for. However, some alternatives for this could be "most brilliant," "most radiant," "most celestial," "most luminous," "most shining," "most glittering," or "most sparkling." These words all describe something that is radiant, bright, and shining, much like a star in the sky. Other synonyms could include "most outstanding," "most exceptional," or "most exemplary," which describe something that is exceptional or stands out among others. Regardless of the word choice, using vivid and precise language can make writing more engaging and captivating for readers.