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A young gentlemen clad in saurus armour passing through town responds to one of the enquiries
I believe I can shed some light on these stones, and the events preceding them.
Was early evening when I and two companions, Sir Benedict of Hoar and Rugnar ventured forth into the crypt to settle the undead in it back to rest. All went well to begin with, and we settled the first level, descending we found the second level strangly quiet, and ventured along, seeking further unrest.
Several fiendish gas traps were triggered, however no-one was crippled by them, praise be the gods, however, then something was heard, and a chill fell upon the tomb
We made haste for the stairs up, only to find hordes of walking corpses pouring down them, bound by far more secure magic to undeath than the usual ones found in the crypt. As the fight went on others began to ooze out of the walls behind us, and around us, but eventually we secured exit from the crypt.
It was then that a strange lightning storm eventuated, with lightning striking but not damging us, and another companion found as we exited, and ground shakes, with the stone circles rising to trap them within.
Some evil in the crypt's had awoken that day, we did not see what, it hid from view and struck from afar, but it settled again to it's slumber.
Mecizq, of Mystra