Any of the three could create a teleport formation for long distances. As for a formation that simply closes a Spatial Gate, in fact, it is even easier to make. They just needed to be careful with the power necessary for that.
Of course, Rean, Zangeshu, and Tanxan knew that the Shadow Beings would try to enlarger the Spatial Gate, so they prepared plenty of Divine Stones to fuel a pretty powerful formation. It wouldn't lose to Kentucky's attempt at all.
As for the killing of the Shadow Beings, they made the formation double-layered. The second one was a Yang Energy-based Slaughtering Formation. To make sure the Formation was going to work, Rean reopened the Spatial Gates a few times, just a tiny gap to allow some Shadow Beings of lower level to come out. During these tests, Rean noticed that the smaller the gap, the weaker the shadows. Obviously, the shadows' sizes were deeply connected to their strength.
