The Linen King by Terri W

In the rain-soaked towers of London, ancient linen meets modern glass. Terri Lynn is Victor Smoke's most lethal asset - precise, elegant, and already carrying a living relic in her thigh. When an immortal king bound in centuries-old linen begins reclaiming his empire from inside a glass skyscraper, she is ordered to dismantle him piece by piece. What starts as controlled attrition becomes a vertical war through flooded stairwells, ritual chambers, and the open air of a storm-lashed rooftop. Every floor costs her more blood. Every kill draws the Linen King closer. He wants the stone. She wants him finished Only one of them will leave the Monolith.