Using their knowledge of the tomb, gained after they had gotten a map out and found out, with a lot of guessing, where the golem nest was, they made it to Samkiel's burial chambers.
They didn't take the corridors, rather, they looked around for the secret passage that was behind a mosaic. None of the adventurers had thought that the Klorfiel family had spoken the truth when they had given the secret passage up.
The dukes of Huergaz were a bitter family. Even more so after Asmodeos had been the one to raise Samkiel himself as a Lich on his way to the Heart of the World glacier.
But, it seemed, the current duke of Huergaz did not want needless death, and, so, he had given up the secret passage. What he had not given up was the sequence in which the colored tiles had to be ordered for the passage to open. So, all the tanks and Morris had taken turns bashing the mosaic until the tunnel behind it got uncovered.
