Against the cult: the Forest Ruin (1.5)

Kragga leads the way up the stairs, followed by Albertus, Theran, and Xana. Joseph hangs back to look at the trap a little more in order to answer Albertus' question, Ogbar is right behind Xana, and Aanbo continues to eye the first floor for any sign of movement (there is none). Then the halfling and dwarf turn to follow the others.

The stairway is narrow and the darkly-stained stairs are steep. Xana is just stepping on the first step when there is a loud "chunk!" from the tenth step (the one Kragga is stepping on, about halfway up) that everyone in the party hears as rusty spikes slam out of the walls of the stairwell in the blink of an eye.

Kragga, make a DEX save with DISADV to avoid the spikes.
Albertus and Theran, make a DEX save to avoid the spikes.
Xana, make a DEX save with ADV to avoid the spikes.

Kragga and Albertus, stuck in the middle of the stairway, are unable to avoid getting hit by spikes, each taking 5 piercing damage. Theran and Xana manage to spring backwards, crashing into Ogbar but avoiding the many spikes that appeared out of the walls. There is just enough space between the spikes that characters can squeeze between them, zigzagging back and forth to ascend the stairs, but there is a clacking, ratcheting noise as the spikes begin to slowly retract back into the wall. You figure that, in about twenty seconds, they will have completely withdrawn into the wall again.

The party moves rapidly up the stairs as the deadly spikes slowly retract back into the walls. Starting from when the spikes have started to retract seems to work; the party reaches the top of the stairs safely, before the trap reset. The room at the top of the stairs opens out to the right and left into two identical wings. Long wooden benches line the walls, a column carved in the likeness of heron-headed Pae stands in the center, and a stone door is in the center of each southern wall. One of the benches, in the far right corner (southeast), may have something on it - some kind of clutter - but the view is mostly blocked by the Pae column.

Creeping closer, Joseph sees that bench bears a bunch of empty glass vials, some of them broken as if they were dropped or tossed down.

"Well know isn't that odd?" Joseph looks around to see if they fell from a height, or did someone just dump them there.

Looking more closely, Joseph sees that the vials have a slight dark residue on them (which Aanbo might recognize), but there is no sign that they were stored higher up. There's no trace of the residue on the bench itself, so he figures they weren't spilled. For all that Joseph can tell, someone emptied the vials and either set or tossed them down.

As Albertus says this, everyone pictures the path they've taken, and all realize that the origin point of the golden light on the second floor was several yards south (and a little bit east) of these stairs, which means that the origin here on the third floor is several yards south (and a little bit east) of where the party is now.
Albertus and Joseph: Roll either an INT (Nature) or a WIS (Insight) check.