Which name do you like better?

i'm writing a book where every night when the sun goes down, the creatures become serpent-like [eyes turn into slits, eyes turn a shade of jade], they have serpent-like desires [striking, sudden movements, ETC.], all of their movements cut through the air as if they were ice, very strong fighters, tough skin [bullet proof but not as hard as granite or cool]. i was thinking or the names Sphyn or Cypernus. Which one do you like better? If you don't like either of them, tell me what you think it should be. Thanks =]