The difficulty of this lock is that the final test remains the same, but the prior four are subject to change. The doors created by the Mechanical Gnomes can be managed, for their knowledge is limited.
However, if the locks are established by the Titans, it is even more terrifying. To decipher the first four nodes is already a tremendous challenge.
Furthermore, the final node is usually the most complicated. Some individuals may be powerful enough to defeat strong monsters, yet overcoming oneself is an entirely different matter.
As the proverb goes, 'It is easier to conquer heaven and earth than oneself'.
This certainly rings true for those who are not adept at battling. For instance, a second-tier individual who lacks combat skills can only fail to use his potential power effectively.