You don't know how the mystery magician is likely to react to being "discovered" like this, but considering that she's meddling with something that might very well be necromantic in nature, you don't want your friends anywhere near her or her impending response. With that thought foremost in mind, you point emphatically at the room which is the source of the shadows, and then wave away from it.
For your troubles, you're rewarded by three blank stares. "Alex," Cordelia says, stalking forward with more clacking steps, "what the heck are you doing?"
Her reaction triggers another spike in the concealed spellcaster's aura. You groan. Clearly, your nonverbal communication skills need work.
Gained Sign Language F
Grabbing Altria's hand, you break into a run, all but dragging the smaller girl along for the first couple of steps before she finds her stride.
"Alex, what-"
"Spellcaster," you reply quickly. "Female, teenager, heard Cordy" - and is apparently hearing your steps as well, now, if the flat-out alarm in her aura is any indication - "not happy!"
That point is driven home when there is a muffled but still distinctively feminine shriek from the room. It's immediately followed by movement from the ki void, a rapid intensifying of the shadows, and then the slamming-open of the door. Silhouetted against an eerie blue glow emanating from the room beyond is a figure of pure blackness, like a man's shadow that has decided to step off of the wall and into the third dimension - save that somewhere in the process, it picked up a set of short, blunted horns, and fingers like daggers. Well over six feet tall and leanly built but for its broad shoulders, the entity seems to wear nothing but its own night-dark skin, yet reveals almost nothing of its physique: no muscular definition; no genitalia; not even a proper face, only a vague suggestion of one on the front of its head, as if the shadow of its skin had been pulled loosely across a skull. It has eyes, though, deep pools of cold blue fire that give off no light, instead seeming to drink it in. A wave of cold that is as much spiritual in nature as physical roils out from the creature as it lowers its head and stalks into hall, and for a moment you swear you can see your breath misting in the air.
Cordelia stops in mid-stride, and for one brief instant, stands face-to-facelessness with the dark entity, staring up at it in shock and dawning horror while its otherworldly eyes looked down at her. Had it wanted to, the thing could have easily seized the girl, and then goddesses only know what would have happened.
Thank all that's holy for Lu-sensei. The instant the door banged open, the old man was already moving, skinny arms closing about his fear-paralyzed student and yanking her clear off her feet as he proceeded to make like the proverbial bat out of hell, colliding with Briar along the way and taking her along for the ride.
"Run, boy!" Lu-sensei hollers at you, Cordelia in his arms and the now-screaming Briar clutching to his sleeve as if for dear life. "Stop gawping and RUN!"
The dark being's light-eating gaze turns in your direction. You feel an alien will clawing at your mind, attempting to drown all thought and action beneath a tidal wave of sheer terror.