Powerful creatures that inhabit the Dragon Sanctuary of Wyrmroost, as mentioned by Agad. Traditionally, they are birds born of fire and at the end of a certain time period they burn themselves up, creating another newborn phoenix out of the ashes. Phoenixes are large red birds, often resembling eagles, that can ignite themselves on fire at will. To some degree like the Sands of Sanctity, phoenix tears can heal almost any wound or injury. Also, phoenixes are virtually immortal because whenever they die, whether of old age or from injuries, they are reborn young and new.
Phoenix flames are one of the only things powerful enough to kill any of the five Eternals.