The Dream Sight divine ability is a useful ability because people are always dreaming.
People are either actively dreaming or passively dreaming. They are actively dreaming when they fall asleep, while they dream passively when they are awake.
Either way, people are always dreaming, and since they are always dreaming, it means that they are always simultaneously in the physical dimension and in the dream realm.
Since they can't meet the killer in the spiritual dimension, they want to meet her in the dream dimension. If they can see her dream, then meeting her in the dream dimension will become possible.
It will even be better if they can mark her dream. That way, she will never be able to escape from them.
The first angel of telepathy doesn't have the divine abilities of the pathway of dreams, which is why the vessel was called over. Once the vessel used the Dream Sight divine ability, the problem of the impenetrable defenses of the fortress was solved.
