Into the Heart of Darkness

As you approach the gate the raged and pulpy remains of several robed humanoid figures appear laying before you.  The ground is muddy and disturbed as if a combat has ensued.  Their bodies look ravaged with flesh torn and missing.  Among their belongings are several holy symbols, a tome, and a small satchel.  

Upon closer inspection of the carnage before the gate, you notice that besides the humanoids there didn't appear to be any tracks leaded up to, or away from the bodies.  A faint trail of blood can be seen leading toward the walls.  Upon closer inspection some of the carved figures up on the walls surface seem to be covered in a rusty read pigment, that sounds out starkly from the carved white marble.  Faint trails can be traced leading heavenward.  You skin prickles as if you feel you're being watched.  

Flanking the main gate are two openings leading down, requiring you to literally 'elbow past' the facade.  A tight spiral staircase leads down twenty feet, notched in the walls are memento mori with time-worn inscriptions long illegible.  The ends of the steps are rounded, as if many before you have made this descent.  

At the base of the stairs are sconces, though the torches they once held are lost to time.  Greeting you in the darkness are rattling of chains and a clicking sound.  

The room before you that stretches roughly twenty feet wide and at least sixty deep.  Centered ten feet before you a pillar adorned skulls in a helictical pattern; with another forty feet beyond it.   The pillars appear to be at least a foot thick. Flanking the walls are skeletons straining at their restrains, chains rattling at their arms and legs.  A thick layer of dust coats everything in sight.  Nothing appears to have been disturbed for a very long time.

Upon further inspection, decayed piles of wood lay at either end of the room, bits of metal glint in the remains, but nothing of value is found.  

Upon further inspection of the room, if the party clears the floor of dust and debris: deep ruts and scraps encircle both pillars.  If there is a light source in the room, one may notice that at several skulls allow light to pass through them.  

A careful inspection of the fresco on the (north?) wall reveals a very faint draft.  Upon manipulating several stones, the wall gives way and slides back revealing ten-foot-wide stairs leading upward.