Presumably a squire under Cyrus, Glenn was a “Knight of the Square Table” who had a notably close, although platonic, relationship with Queen Leene. He later witnessed Cyrus’ death in the hands of Magus, and was shortly after transformed into an anthropomorphic frog by the dark mage. He was then known simply as “Frog” or “Kaeru” in the Japanese version, and Glenn dedicated his life to his Queen, vowing to avenge Cyrus by killing Magus.
It’s interesting to note that this is Negative Dreamer’s real hair, first dyed blond then dyed green. Now that’s what I call dedication! Thanks to Vanessa for suggesting this!