The term 'mythical shield' can be summarized by the crossword solution 'AEGIS', which is a five-letter word. In Greek mythology, the AEGIS was a shield associated with Zeus, the king of the gods. It was said to be made of goatskin and was often depicted as being covered in scales and having a head of Medusa on the front. The AEGIS was believed to have magical powers and was used to protect Zeus and his family from harm.