The cultivators who had fallen in front of the stone steles had fallen because their bodies were too weak to bear the sword intent in the stone steles.
By the time they reacted and cut off their wrists in an attempt to escape from the stone tablet, their minds had already been invaded by the sword intent. There was nothing they could do to save the situation.
This also explained why there was lightning in the ancient formation. It was for cultivators to temper their physical bodies and allow them to last longer.
As for the last stone tablet, it was the place for sword cultivators to verify their Dao. They could engrave their sword Dao on it, and after passing the test, they could exert ten times the power.
Li Tian was relieved after he figured this out. He walked straight to the largest stone tablet and adjusted his state of mind.