—Azura in Heirs of Fate 3
Cadros is an unseen character from Fire Emblem Fates, first mentioned in Heirs of Fate 3. According to Azura, he was a friend of Anankos and the first king of Valla, and could sing the 4th verse of Lost in Thoughts All Alone. His descendant Shigure is said to have a resemblance to him, and Anankos repeatedly mistakes Shigure for Cadros in the later stages of his insanity.
Cadros could come from Belatucadros, a god who was worshiped by people in Celtic northern Britain, and was identified with the god Mars in Roman mythology. Belatucadros means 'fair shining one' or 'fair slayer'. In Galician, cadro can also mean 'painting,' possibly referencing his similarities to Shigure. The Latin root "cad" means 'to fall', and the Latin word "ros" means 'moisture' or things having to relate to the sea and water. As such, Cadros can mean "falling moisture," referring to rain.
His Japanese name Ryuurei (流麗) is a Japanese adjective meaning "elegant". It could also be read as "dragon spirit" (龍霊).