"A Ghost and Four Keys" is the third episode of the first season of the first installment of the Voltron franchise, Voltron: Defender of the Universe. It originally aired on September 12, 1984. The series this episode is from is based on (and essentially an edited and dubbed version of) the Japanese series Beast King GoLion.
Keith, Lance, Sven, Hunk and Pidge ask for help from the Princess Allura to find Voltron. With guidance from the ghost of her father, King Alfor, they find four of the five keys needed to form Voltron. With no choice, they head into battle with only their robot lions to keep back Doom's soldiers.