Ran's shikigami will find a lot of darkness and dust in that air vent. The glow reflects off something slick and red that writhes back like a coiling snake... is it afraid of the thing's light? Or...

Meanwhile one of the scientists pipes up:

"What makes you so sure there's just ONE of them?"

The darkness gives an answer, not from the direction of the air vent but from down the hall. A glimmer of the same slick red, like a blood clot that hasn't quite hardened, but this one completely free and shaped into a beastlike thing that skulks forward on four oozing limbs.