Howling Tombs

The group saw a vast cave with multiple passages around the cavern with numbers on top of each cave passage. There were a total of 10 cave passages and ten numbers, from 1 to 10.

"The numbers indicate the difficulty."

After Lilith finished speaking, Erix created a portal connecting to their cave.

A few other people were waiting while sitting, talking, or training in this cavern while their companions or subordinates went to challenge Tombs. 

They were surprised to see Erix creating a portal and noted the group.

Afterward, Lilith and Reinala stayed at the portal while Erix, Rin, Lily, and Klelia went to the level 1 cave passage.

After entering, they saw three tombs and no people.

Lily walked ahead and said, "These are three level 1 tombs here. We have to touch one of them, and it will absorb us into the battlefield, where we'll fight a challenging individual."