The windless state of this side of the world generally lasted a few days every time, and several times each year. It so happened that the one time Althea visited, she experienced it while she was out in the open.
The cave was not airproof, and they certainly would still want to breathe, so the monsters would inevitably have an idea where their 'food' was hiding.
They'd even find ways to dig. The other holes were okay; they were rocks, and the openings were small, uneven shafts with two ends far apart, so even if the monster dug a ventilation hole from the other end, it would take them a long time to reach their side of the shaft.
BANG!
BANG!
That was just applicable for the ventilation shafts. The main entrance, barely blocked by Althea's earth wall, was too big and definitely not stable enough to last half a day.
It had only been an hour, and Althea could already see cracks at the top corner of the wall. The windless period would last days.
