Here There Be Dragonnes

Thing was a young girl who hid beneath a mask. Her companions included a crow, a toad, a goldfish, and a kitten. Never was there a more unlikely band of unheroic heroes. Yet she had a ring with unusual powers. . . . Summer was an orphan who owned nothing -- except a certain ring that would lead her to find a unique love. . . . Sophie was cast adrift in London by the untimely death of her parents until an uncle left her a legacy -- if she took a dragon's egg into uncharted Asia, with the help of a certain ring. . . . Three very unusual heroines in widely separated times, each wearing for a time a ring made from a unicorn's horn, a ring with very unusual powers. . . .