The entire thing might be depending on the heart William made and the mountain backing it up, however there was something else that was needed; a controller!
The controller would be governing over everything happening between all these formations. As the heart was going to suffer from hellish pressure, the controller was going to suffer the same.
William knew this, and that was why he took out tons of healing elixirs, much more than spirit regeneration elixirs.
The first few minutes would require him to spend tons of his spirit power, but later on he wouldn't lack any spirit power anymore. In fact, his suffering would start when he'd face immense spirit power, one that he wouldn't be able to handle.
His body would suffer lots of damage, and he would spend lots of time healing and repairing his body than controlling the formations.