Enterprise emerges from a cloaking barrier
A cloaking barrier was a large energy field that encircled each of the Delphic Expanse spheres, used to keep the spheres completely invisible and hidden from outside observers.
The barriers were extremely energetic and hazardous to ships traversing them. The first time the Enterprise NX-01 entered one of the barriers, it suffered power fluctuations and microfractures along the hull. (ENT: "Anomaly")