The word "fantasticalness" refers to the quality of being imaginative, whimsical, or fantastical. Synonyms for this word could include "fancifulness," "imaginariness," "dreaminess," "unreality," "fictionality," "fantasy," "mythicalness," and "make-believe." These words all evoke a sense of wonder and otherworldliness. They are perfect for describing a work of fiction, a vivid dream, or an artistic creation that transports the audience to a different realm. The use of these synonyms can help to elevate language and create a more magical atmosphere in any creative work.