The Rainbow Phoenix is one of four pets that appear to fly when they move.
Anomaly! The Rainbow Phoenix's attacks are hugely out of sync with its attack animation. It usually strikes the opponent after completely swooping back from an attack.
Historical note: For a short time after the 4th Anniversary Update that introduced the Zaishen Menagerie, there was a bug that made it possible for heroes to charm this pet. The bug was quickly fixed, and all Rainbow Phoenixes on heroes were removed.