A plan took form in Lex's infantile mind. His plan was based on the level of confidence he could summon up on his own ability to survive hazardous conditions. After a moment of contemplation, Lex was fairly confident that he could survive - not that these tests would kill him anyway.
With his plan set and decided, he continued to put up various defenses while specifically avoiding having any that contained spirit energy. After all, this particular type of lava, or fire, seemed to burn it right up!
These defenses included, but were not limited to, arrays that specifically absorbed heat energy to work, space barriers, compressed stone and walls of supercooled rock which were cooled through the use of arrays.
No sooner had he finished that a massive earthquake came, much stronger than the ones he experienced before. Before the tremors had an opportunity to subside, a massive explosion rocked the entire tunnel network, shaking even the burrow Lex had created.