Achaierai
The Achaierai is a large sentient monster bird from Dungeons & Dragons. They were originally Chaotic Evil beings during the Advanced Dungeons & Dragons days, but in third edition they were retconned into always Lawful Evil and are considered outsiders that hail from Acheron. This seems to have been kept for fifth edition, as Minsc and Boos Journal of Villainy uses the newer alignment and origin location.
They have spherical, feathered bodies, with no neck, tiny wings, and four long metallic legs. An Achaierai can't bend down properly to attack grounded folk, so they swipe their legs as their main attack, and they could be crippled if these legs were too injured. Their legs regenerate after a few days, unless they're fully cut off. Despite prior lore and statblocks, the Journal of Villainy states that they can in fact bend down enough to properly attack using their beaks. They can also release poison smoke, which also causes non-Achaierai to also go down with madness and confusion.
They are carnivorous predators that like to torture others. They seek vengeance against others who had a slight against them, but turn against themselves during times of trouble, despite normally going in flocks of two to eight.