Ephflynne

Ephflynnes are enormous creatures that swim through the air at thousands of miles per hour. They're normally completely translucent, but they are able to change the wavelength of light they reflect to blend in with their surroundings or to make themselves visible. They eat massive amounts of vapor every day, which they track and locate by following a pheremone known as sugreth. An ephflynne can grow to be ten miles long and can live for hundreds of years.

they are enormous creatures that swim through the air at thousands of miles per hour.