Just as Du You had previously had the Death Ape help dig a hole, the two sisters had also made preparations in advance.
If they directly retreated into the hole, the boarmen would see them. So the sisters thought ahead and placed the coordinates for the space transitions inside the hole beforehand, and then destroyed the entrance from the outside.
They then did a little camouflage to make it undetectable by the enemy. Because the spatial transition used by the sisters did not consume much magic power, they could still use it even when they had only a little magic power left.
In a flash, the two of them appeared inside the hole, leaving the skeletons on the ground who had lost their command to continue resisting the attack of the boarmen. And the crazed boarmen did not even notice that two of their opponents were missing.
Perhaps in their simple-minded heads, they assumed that these two individuals had been dealt with by their companions.