Whatever it was, it wasn't subtle.
The door groaned once, then curved inwards like a balloon. Black ichor dripped from its edges as purplish veins rippled along its white wood. The knob blackened and slid towards the middle of the surface, its keyhole weeping a steady stream of blood. What had once been a door now was a gigantic, shivering eye.
He stared at it staring at him until he could deny it no longer. Then he hid his face in his hands and huddled in the furthest corner.
It was the only way out of the room.