Dungeon below the Ziggurat

As you descend into the depths of the old dungeon, the air becomes thick with moist, and the flickering light of your torches reveals crumbling stone walls covered in moss and mold.
In one corner, what seems like a large blood vessel sticks out of the wall. The veins seem to pulsate with an otherworldly energy, casting an unsettling glow on the surroundings.
You're suddenly aware of sound that you can hear, ever since you've entered the first room. It is of a slowly beating heart.