There is a narrow, rickety staircase leading up. Dust coats the steps and rails, and cobwebs seem to fill every nook and cranny available. There are no windows and the staircase is dark.

Does the staircase a) look real, and b) look like it would collapse under weight (investigation: 8)

You feel like it's pretty real and would totally hold you.

Uri throws a single caltrop up onto the stairs. If it lands ok, he advances up and picks it up on his way past. 

Perception 12 

The caltrop lands just fine. The stairs creak and groan as you walk, but hold up under your weight.

Aluchard is going to follow Uri as well.

Terrick will wait until they are a few steps up and flow as well.

Zephyr will walk up when no one else is on the stairs 

As you're walking up the steps, Eden notices a seventh set of footprints in the dust walking up with you.

As Eden waits for the Zephyr to walk up and she notices the footprints, she calls out to the others.

"Uhh. Is it just me or is there an extra pair of footprints following us?"

On the landing, Uri takes a few steps forward, then a few back, then launches into a dominant Pasodoble, certain that their invisible companion will neither be able to resist joining in, nor keep up.

"Ghosts can't dance!" he announces, performing a (adverb depends on the roll) pass ...

Performance : 12

....before sliding in for the kill with a deep dip that will render anything but an unfeeling ghoul breathless.

Smoulder : 24

You pull off a smoldering smoulder, and a lovely little dance, but nothing joins you. The footprints go all the way to a door at the top of the stairs.

Aluchard claps for the dance and then approaches the door where the footprints go and opens it.

Terrick stares at the dancing on the stairs.  He scrunches his brow in confusion and then ignores the desprate cry for attention.  He will take his magic sword and poke at the space with the phantom footsteps are.

Zephyr makes it up, "Have you gone crazy Uri, this is not the place for dancing!" 

"Where you hear a heart beat and blood pump, it's a place for dance. It's what separates us from them. Now... let's investigate that door. Arms ready?"

Thaumaturgy to throw open the door the footsteps end at, from a distance.

The door opens into a large common room with a fireplace taking up most of the south wall, with doors to the west and north.

Uri creeps forward towards the door then - twisting the little salmon signet on his ring - leaps into the middle of the room, resisting the urge to shout "Ha - ha!" on landing.

The floorboards creak a little when you land, but you also hear a low moan come from the fireplace when you land.

(did you mean the west and north? Or should the west door be open and the east door closed?)