The entrance to the cave was larger than Karl had expected, not much of a "hidden cave" and more of an "obvious natural feature" sort of place.
If you could walk five people shoulder to shoulder through the opening, or let Rae walk through in spider form, you were not keeping much out of your safe space.
However, once they got a bit further in, there was a choke point, just wide enough for one person to pass through.
It was small enough that Rae would have struggled in spider form, if she didn't have the ability to simply pass through the stone, or teleport past it. That would keep out some of the larger monsters, at least.
Enough that the groups hiding in here could rest a little easier, and small enough that they could set a barrier to block the door if necessary.
