The universe is thinning. Slowly. Imperceptibly. As the universe dies, so too do the walls preventing the other universes from getting in. Do you understand? Let me explain.
This galaxy is part of a universe, a vast collection of galaxies existing in a 4D space, the fourth dimension being time. Now imagine, for a second, a collection of 2D boxes, drawn on a piece of paper. We can collect all these boxes together by drawing another 2D box around them. We can imagine your planet as a 2D box. The 2D box collecting them is your galaxy. Yet another 2D box collecting all the boxes containing boxes is the universe. However, we can also collect these boxes in 3D. We can imagine a cube, into which we place all these boxes. And since the boxes have no width, we can place an infinite number of these 2D boxes inside this 3D cube.
If we imagine that these 2D boxes are universes, the 3D box is the multiverse, a container which can contain an infinite number of 2D universes. Now universes exist in 4D, but there also exists a box of 5D, containing all of the universes. We can refer to this 5D box as the multiverse.
As the 6th dimension changes, that being the dimension equivalent to time in 5D, the five dimensional box changes. And as it changes, the 4D universes are jostled a bit. The rub against each other and on there edges we can detect friction. And as change increases in the 6th dimension so too does the energy added to the universes through friction increase, until the universes start to melt together.
Now, I will admit, the language this universe has developed will not quite grasp these concepts. They are difficult enough to understand while trying to use a language designed to indicate to other monkeys were food may be found. However, hopefully you get the gist of it, because my message is important.
The multiverse is slowly melding all the universes. Those universes in the middle, packed tightly together, were the first to meld. And as the universes meld unspeakable creatures travel from one to the next. You can imagine it yourself. Here, everyone looks like you, but in another universe you are a creature of nightmares, a bedtime story written by madmen who have glimpsed what the multiverse holds.
You are lucky. This universe lays near the edge of the multiverse. However, a great danger awaits you. For in the melding of the universes there has come a creature from some desecrated world which is as old as the multiverse and quite capable of bringing about the apocalypse. With it comes its strange race, entities of energy made flesh and geometries impossible to describe. I do not know what they are. I do not understand even how they can exist. Perhaps they are the beings which live in the fifth dimension. Perhaps they are the result of some catastrophe which causes them to exist in a different form then typical life. I do not know. All I know is that the great black universe they have created is expanding, consuming universes as they meld together. And your universe will soon be threatened by them. It will take thousands of years for the friction to finally breach your universe, but it has already begun. How else do you think I got in?
At first, there will be only a few of them, sowing discord and lending truth to the old tales. But soon they will come. Make your peace humankind, and ready your armies for a foe beyond anything your brains can even comprehend. Watch for there arrival. Search for them in the stars. Because they will come. And they will destroy you.