Terrifying creatures exist there who could kill any Star force realm cultivators just by breathing. As much dangerous as that place is, it could also be called cultivation heaven for people. The Effectiveness of cultivating in the dark universe is almost hundred times that of the main universe. The problem is if you start cultivating there it'd attract those dangerous creatures to you. Even if you were able to defeat one, two, a dozen of them more would be coming to you. Eventually, you'd be exhausted and would die. That's why no cultivator dares to go into the dark universe to cultivate. The time flow is also differs between the dark universe and the main universe almost by an average of 1:30. So if you spend 30 years in the dark universe only 1 year would've passed in the main universe.