This Dragon is obtained for completing goals.
This Dragon is only released for a limited time during it's associated holiday
For a limited time during an unspecified window of availability. As a prize in the Spin to Win game (iOS only).
The phrase 'vain as a peacock' most likely originates with Blue Peacock Dragons, but if they have swelled heads, it's not entirely their fault. Their caretakers frequently go on about how beautiful their plumage is, leading to overlarge egos as a result.