I think what we have here is a mirror of transfixion. Basically, if you look into your own reflection, it paralyzes you, then traps you, or your soul, cant remember which, inside. I remember hearing about it when i visited the Underdark as a small child.
As long as you don't get too close, and dont look into the mirror, we should be safe. Cause i swear, that reflection was not moving with Grahf as he passed by, it was looking right at him even as he was moving across and not looking at it.
If im right, we might have an exelanation for the dissapearances, and why this town is desolate and abandoned, yet the children only claimed two days had past. Either the original messenger, amd children escaped somehow, or the mirror purposely let them out to lead further prey here to trap within. 🤔