Imagine the following.
Up on the twelfth floor, the rain gently pitter-patters against the windows of your apartment. In the distance across the dark sky, a thunderstorm is brewing. It's late. Too late. You should have been in bed already.
You sigh as you force yourself up and off the couch. Then, just as you turn off the lights in your living room, a bright flash of lightning illuminates the sky and it is in that brief moment that you see it. There, out on your balcony, pitch black against the bright background, the silhouette of a horse.
It only lasts a moment. As you blink and look again, it's gone. You hesitantly approach the window, but your balcony is abandoned. Dismissing it as a play of the light, you go to bed.
That night, your sleep is restless.
The next day, you step out onto your balcony for your morning smoke, feeling the dirt and sand under your bare feet. You've neglected cleaning here for years. As you casually glance down, you see them. Unmistakable. Your hand twitches as you take a long drag of your cigarette, your gaze transfixed on the patterns in the dirt. Hoofprints.
It confirms what deep down you already knew to be true. Your eyes were not deceiving you last night. He was here. How he got up here, you can't explain. Nobody ever can. But he was here. And he will return. Now that he has marked you, there is nothing you can do to prevent this.
You may have days, weeks, even months. But eventually he will return. The black horse who's name you dare not speak even though it is filling your mind's eye at this very moment, blocking out your senses as the cigarette drops down from your numb fingers.
Soon, as your sanity is slowly stripped away from you, his name will be the only word left that still holds any meaning. It will be the last thing you ever think of, blind as you will be made to everything else. In the end, you will welcome it. You will embrace it as much as it embraces you, permeating your very being as your mind flickers out of existence.
Then, only darkness.