Day 2

Thorem walks up the stairs to the top of the structure, he knees an touches the floor of the structure and recall that building structures from stone blocks of this this is used for monumental building basements or tomb: even if there are any "rooms" inside that structure it is primary build to stand forever, not to be a functional building.

When Bellow touch it with glaive the color it is shining with changed to green color.

When Bellow finish saying that the color returns to white

A small fix: the 3 pillars on the ground are also shading white light just as those on top of the structure.

Thorem understand that build principles are trivial. It certainly not build by dwarfs based on the quality of sone blocks. But anyone could have done it, even goblins or orcs. The biggest question is - how this big stone blocks were moved here, they each are of size 2.5x2.5x2.5 feet. Most probably magic were involved.

There are 5 pillars shining and two chests similar to one down. These chest are of better condition - only is only slightly cracked and you see gold inside, probably also fake one - but hard to tell crack is not fob enough.

When Thorem moves down the corridor he see it ending in a hall with stairs down into the water

When Bellow touch pillar it changes colour just the same way as previously and turns back several seconds after released. It does remind you of a tomb where floor segments behaved in similar way when stepped on, thus letting guards to detect intruders more easily. You could also recall that the length of the signal would increase every time it is touched repeatedly to inform about number of intruders.
But when Bellow try to test this and it touching pillar repeatedly - it does not seem to increase the time the green light is on.