Ash Pheonix

A massive raptor made of ash and shadow screeches as it dives, its eyes like glowing coals. Impossibly, it stops its dive mere feet from the ground, and its powerful wings whip up ash that carries the chill of the grave. Ash phoenixes are the animated ashes of mass funerary pyres, which seek the eradication of all life around their birth pyres.
Cremated Birth. For an ash phoenix to be created, a group of humanoids must be burned in a mass pyre in an area tainted with necrotic energy, and the blood of a magical avian, such as an august rooster (see page 33) or firebird (Tome of Beasts, p. 201), must be mixed into the pyre as it smolders. Necromancers often follow the armies of warring nations in secret, with the blood of a magical bird in hand, for the chance to create such powerful undead. Unfortunately for the necromancers who create them, ash phoenixes are nearly impossible to control, often leaving the creator as the phoenix’s first victim.
Disturbed Souls. The creation of the ash phoenix disrupts the natural passage of souls into the afterlife, infusing the phoenix with the angry spirits. The presence of these spirits gives the ash phoenix some level of intelligence but also drives it to seek vengeance against all living creatures. Ash phoenixes never stray more than a few miles from their birthplace and are reborn in those same ashes each time they are slain. To end an ash phoenix’s reign in a region, the original site where it was created must be purified and the souls properly put to rest, usually through performing burial rites and casting the hallow spell at the site.
Undead Nature. The ash phoenix doesn’t require air, food, drink, or sleep.