Chalkydri (Ancient Greek: χαλκύδραι khalkýdrai, compound of χαλκός khalkós "brass, copper" + ὕδρα hýdra "hydra", "water-serpent" — lit.
"brazen hydras", "copper serpents") are mythical creatures mentioned in the apocryphal Second Book of Enoch from the 1st century CE, often seen as an angelic species.
The chalkydri and phoenixes are described as creatures 900 measures in size with the head of a crocodile and the feet and tail like that of a lion, each having twelve wings, and are empurpled like the color of the rainbow.
[3][4] At sunrise, all the chalkydri break into song with their counterparts, alerting the birds of the world for a new day to rejoice.
Similarities to the story of the chalkydri and phoenixes mentioned in the Second Book of Enoch can be found in the Greek Apocalypse of Baruch, which mentions a story of Baruch seeing a large bird flying around the Sun said to guard the Earth who an angel identifies as a phoenix.