The term 'mythological bird' can be summarized by two crossword solutions: ROC (3 letters) and HALCYON (7 letters). A ROC is a giant mythical bird of prey from Arabic mythology. It is said to have the ability to carry off and eat elephants. HALCYON is a mythical bird from Greek mythology, often associated with peace and tranquility. It is said to have the power to calm the wind and waves during the winter solstice.