Regardless of her approach, Ciri will find a small metal container. It's dented, but opening it will reveal a highly flammable powder. They may want to save it for the right moment.

If she chooses to look into a narrow space using Castiel's burst of strength, the disturbance will cause a large rock up top to fall down. They will need to be quick to avoid it.

If she chooses to climb higher, one of the tendrils from the Bone Serpent will reach down and try to grab her. With Castiel's help, she'll be able to escape.