Tenorio's eyes show the madness and obsession that are driving him by the novel’s end, which Anaya portrays to frightening effect through visual imagery and metaphor. Antonio catches Tenorio’s gaze while standing near the place where Tenorio killed Narciso, and the moment fills him with fear:
His blind eye was a dark blue pit and the other glared yellow in the dust. He laughed and howled as he looked down at me and I thought he was drunk.
The imagery of Tenorio's "dark blue pit" of a blind eye and the "yellow glare" of the other is deliberately frightening. The "pit" makes the reader feel a sense of emptiness and danger, as though Tenorio’s lust for revenge has literally hollowed him out. The "yellow glare" of the other eye suggests that it's unnatural or diseased, which makes Tenorio seem even more menacing. It also underlines how predatory Tenorio is, as yellow eyes tend to appear in flesh-eating animals and birds. He also "howls" like a wolf when he laughs. Given all of this, Antonio feels extremely vulnerable when fixed with Tenorio’s gaze.
The metaphor of the blind eye as a "pit" conveys more than the eye's appearance. By this point Tenorio has no humanity left, and his eye is a visual representation of the void his actions have created within him. The “blind eye” physically evokes Tenorio’s expanding capacity for violence and remorselessness. His two contrasting eyes reflect the reasons for his actions. One part of him—the “blind eye”—is consumed by guilt and emptiness. The other eye, predatory and yellow, is awake and has agency. Both "eyes" are driving him to kill, propelled by his anger and cruelty.