The entire thing so far was about invading the Werdlem Universe again. However, it would be easier said than done. Any Abyssal Path leading to the Werdlem Universe would be under constant vigilance. Not to mention, all these paths connected to the same place in the Werdlem Universe, so using them was pretty much suicide.
That's when the idea of stealing a Great Void Spaceship came about. The Werdlem Universe was also protected by Universal Formations, which was to be expected from a Universe with such importance. That means, when the twins' group tried to enter it from outside, they would still be detected, if they could enter at all.
The twins' group was willing to use that method anyway. All they needed was to get inside, then use their own Spatial Gates to leave the area. So what if the Werdlem Empire found out that they had entered the Werdlem Universe? As long as they couldn't be tracked, it wouldn't be an issue.
