There were still many crimson slimes outside the Hall of Closed Cultivation, but at least their movement was not as restricted as when they were fighting in the building.
Not to mention, the Hall of Closed Cultivation was not an ordinary building.
It was built from many special indestructible materials, such as a thousand-year-old rainbow steel ore, earth crystal core, and so on.
The building was made so that no one could break into the Hall of Closed Cultivation and interrupt them at the critical moments when they were having breakthroughs to a higher level in their cultivation.
Taoist Uncle, as the High Rank Spirit Transformation Stage Grandmaster, was the person who was restricted the most inside the Hall of Closed Cultivation.
