Apollon

while most unicorns appear to human with pure hearts, apollon draws in people with Darkness.

once a lustrous white color with a silky coat, now he is a dark violent with stringy hair. his hair is constantly falling out, and he is perpetually emaciated. he is constantly in a state of suffering. negativity causes his lungs to fill with fluid and his eyes to crust over. things only get worse when he encounters humans, which isn't uncommon as he is like a magnet to those full of hatred and vitriol.  

he is hounded by hunters who want to cut off his horn and sell it for a high price. unfortunately for apollon he is immortal, so all their knives, axes and arrows mean nothing to him in the long run.

if any managed to actually catch him and cut his horn they would be in for a surprise however. unicorns possess great healing magic if caught by a virgin, but apollon's horn would theoretically cause a plague if consumed.