Something readers don't give enough attention about the Watchers...
Invasion of the Watchers didn't work flawlessly.
As some enterprising Watchers openned a rift to the universe, they went through the rift and they felt pain, time and heat in the Void. But something happened, during travelling between dimensions, rift is closed. They did not know the reason, but they were certain they are betrayed. They again felt cold and became lost in dimensions, frozen in time.
What was the reason? Why would they betray each other? Why would they close the Rift?