Prince Woeus is an Equestrian Natural Alicorn, and the Alicorn God of Fear, Suffering, Black Magic, Darkness, Torment, Pain, And Ruin. He was one of the many Alicorns that ended up going rogue and had to be defeated like Mortuus, Death Coffin, Lord Order, and Lord Chaos. He is the father of all dark apparitions before the arrival of Pitch Black, and created not just the umbras that corrupted King Sombra, but also the father of all Taraxippus, creatures or ghosts based on Greek mythology that scared ponies and were the previous image of the boogeyman before the arrival of Pitch Black. He was defeated by being turned into pure shadow forever, and being manifested into a shadow realm for his Taraxippus creations to be banished to. Millennia later, Pitch Black arrived in Equestria after seeking power since his reign in the Dark Ages of his world was destroyed and he was never believed in, and sought to be believed in on other worlds, and he found it in Equestria, where he discovered black magic, and thus tied it to it's father, Prince Woeus, which guided him to Hollow Shades, the former homeland of Woeus, and he found a gate to the shadow realm through his home, the Woe Hippodrome where Woeus tormented ponies until they died of fear or committed suicide and became Taraxippuses, and helped choose several Pony of Shadows, which was the Taraxippus' ultimate fearmonger, one of them a tragedy-destroyed mare named Doldrumsta Blue, who served as the Pony of Shadows for the remainder of the Great Fear War, until she was freed thanks to the heroic achievements of Halo Epiphany, and then finally Halo's brother and the recently-abandoned protégé of Starswirl the Bearded named Stygian, but not before he was finally defeated and swore to return in a future generation ripe for a new fearmongering. Stygian, as the result of stealing relics from his mentor for being underappreciated since he got him and his Pillar allies together through first stopping The Dazzlings after he was lost of all hope, and being punished for it blindly by Starswirl, he sought revenge for being left in loneliness once again through the Taraxippus in Hollow Shades upon arriving at the Well of Shade, where he became the new Pony of Shadows, and have is former friends cast him, and themselves, to limbo, a space between worlds where no time existed and anything inside was stilted, halting their aging and disappearing, and yet still banishing the Pony of Shadows. Since then, lies of the Pillars' disappearance were fabricated by the dark remnants of the Pony of Shadows to eliminate all the hope they left to repair Equestria from the Fear Wars, and thus it resulted in many events including the formation of the Union for Non-Pony Creatures, as well as Celestia and Luna's fears of losing a family member, friend, or idol to darkness to come true when Luna wished Starswirl good riddance after how he treated Stygian, and not helping with the disappearance of their parents, King Nightus and Queen Heavenslight, as it slowly resulted in not just the creation of Nightmare Moon, but also the Tantabus through her, as well as the creation of another menace in the form of Bishop Dipper. This history proved clearly the raw power and terror Prince Woeus himself was capable of.
Woeus is pure fear and hatred incarnate. He has unlimited access to black magic, he can shapeshift into the most fearful forms, he can debunk mental defenses and induce negative emotions into people, can induce hallucinations of worst fears, can turn different races against each other, can bring out and unlock the worst in people, can corrupt or mind-control people, and he can torture at his leisure.