Diamkey

The freezing rain pounded the roofs of Dark Alley, washing away the soot and sins of the old city. In one of its darkest alleys, where even the reflected light of the neon signs did not reach, stood two people.
Cap leaned against the damp brick, calmly rolling up the sleeve of his leather jacket. His movements were precise and measured, habitual. On the contrary, Diamkey froze, pressed into the shadows, as if trying to become part of them. His pale, perfectly chiseled face was distorted not by hunger, but by agony. The agony of expectation and shame.

"Come on," Cap said calmly, showing his wrist, which was covered in a network of old scars that looked silver against his pale skin. "I'm not here for the evening, I have a patrol in an hour."
Diamkey took a step forward. His eyes, dark-dark, like two abysses, shone with an inner scarlet light.
"I hate this," he hissed, his voice like the creaking of old wood. "I hate this need. I hate myself in these moments.

• I know, - the Xenomorph smiled briefly and without malice. - That's why I'm doing this. So that you only hate the moment, and not those who could tear you apart in a fit of hunger.
  They stood like this every month. The captain was the city's guardian, a man with an old secret. A wound he'd received a decade ago from an artifact belonging to an ancient witch had changed him forever. His blood was no longer just blood. It regenerated at an incredible rate, renewing itself like a lizard growing a tail. He was an eternal source, a living spring.
  And Diamkey is a vampire of the Old Blood, one of the last of a clan that once swore not to hunt humans, but to find another way. A way almost impossible. They died out, going mad from hunger or throwing themselves into the sun in a fit of despair. Until Cap found him about twenty years ago, mad and ready to break his promise.

Cap extended his hand.
-Come on, old friend. Don't keep me waiting.

Diamkey moved with inhuman speed. He did not bite him. That would have been too brutal, too intimately humiliating for both of them. He ran a sharp claw across his wrist.