Harpies are a very dangerous enemy seen in Phoenotopia and Phoenotopia Awakening. Along with Arcs, they are one of the breeds of mutant supersoldiers that were created during the Great War as a prototype for the Phoenix Weapons; as such, they are extremely powerful and difficult to fight. There are also friendly Harpies that can be found in the Hidden Village.
Harpies are humanoids that are hybrids between a human and a bird. All enemy Harpies have pink feathers, though the friendly ones come in a wider range. They only appear once as a miniboss in the Phoenix Lab but are more commonly found in the Forgotten Forest. They have very high health and a variety of dangerous attacks. In one such attack, they shoot spreading needles from their feathers. In the second attack, they will fly offscreen and then return carrying a Rollo Mine which they will try to drop onto you. With speed and precision, it is possible to use the Slingshot to shoot the mine and kill a Harpy while it is still holding it. This will also earn you the Harpy Backfire achievement.
In the final attack, they will divebomb at Gale, which can do heavy damage but can be easily dodged by moving away as the Harpy comes down. A Harpy will signal a divebomb by flapping her wings faster and then pausing for a moment before commencing the dive. The Harpy will dive lower than Gale's position and then slowly fly back up, giving a window of opportunity for her to attack the Harpy.
In the Hidden Village, there are friendly Harpies that appear as NPCs that Gale can interact with. Some will be suspicious of her due to her being human, while others will take a liking to her for various reasons. A pink-feathered Harpy, for example, took a liking to Gale due to her matching pink hair. Another younger Harpy befriended Gale when learning that she too dislikes water.
In Phoenotopia Awakening, Harpies are slightly tweaked in both their appearance and attacks. Their spreadshot needle attack is pretty much the same, but they also carry scythes that allow them to deliver a variety of melee attacks as they divebomb Gale. And when they fly off to grab something to drop on Gale, they now sometimes bring in rocks or crates instead of Rollo Mines.
The remake will very likely feature NPC Harpies as well.