The Omen

The Omen is a mysterious figure who haunts Jack. A being that helps leads Samurais to their end. He resembles a ghostly black silhouette of an armored samurai with glowing eyes riding a horse, surrounded by an ominous green fog. He has a deep, dark voice.

Background
Very little is known about the mysterious Horseman, except that he stalks Jack at various points; it can be noted that he always appears whenever Jack has feelings of intense guilt or doubt in himself.

The Horseman first appears on the other side of a stream, after Jack hallucinates seeing his parents and multiple corpse-like people. The area becomes black and the rider appears with a ghastly green background, shocking Jack as he glares menacingly at him. The Horseman appears again that night, as Jack is tormented by a hallucination of his Father in flames, after which his signature horse whinny alerts Jack to turn around and see the Horseman again, imprinted on a rock. The next day, in the middle of Jack's battle with the assassin Scaramouch, the Horseman appears on a nearby hill, watching Jack's hallucination of the city's slain children.

Later, the Horseman appears a fourth time as Jack hides inside the parts of a previously destroyed Beetle Drone. As one of Jack's hallucinations of himself pleads with him to "join his ancestors", Jack turns to look through the crack of the Beetle Drone's shell, only to see green mist surrounding the area and the Horseman staring at him. Jack manages to see past the Horseman and his misty fog, therefore finding a temple to seek refuge in.

After being grievously wounded and narrowly escaping from the Daughters of Aku, Jack tries to find shelter in a forest, only to turn around and notice the Horseman waiting for him. Jack tries to ignore the spectre, but discovers that its mount can move. As Jack continues his search for shelter, the Horseman refuses to be ignored and continues to stalk Jack while still on horseback, never taking his eyes off him.

Inside one of Aku's factories, The Horseman seemingly claims victory as he notices Jack's grief over the unconscious kidnapped children (who Jack believes to be dead) and speaks to him for the first time, telling Jack "It is time". A broken Jack simply answers "yes" and follows the Horseman out of the factory, leaving Ashi and the children alone.

In Episode XCVII, The Horseman is discovered by Ashi encouraging Jack to commit suicide with his ancestors watching. He attacks Ashi when she tries to stop him, but Jack intervenes and duels the Horseman. After a brief fight, Jack vanquishes him and his disappointed ancestors return to their graves.