If you go out to the edge of the universe and go beyond that you reach the void. and if you go beyond that you reach the abyss.   This is where the Abyss beasts live. extremly hostile and dangerous.    

Fallen Abyss Beast

  Abyss beasts sit on the outside of the Universe and very rarily they will on accident find a way to get in. most that get through are around 2 - 3 every thousand years and they just float around. if they do get to a planet they will most likely destroy it since to normal people and creatures it means death. This has thankfully never happpened but a name was given to the ones that got through. The Fallen Abyss Beasts. there is also the fact they can be seen when in the Universe. They look like 3D shadows or a spot of void shaped like some kind of creature. most of the time you wont be able to tell if its faced toward you unless its heading your way and if you are not prepared or even if you are prepared they mean instant death they come in many diffrent shapes and sizes.    

Awakened Abyss Beast

  If an abyss beast ever lands on a planet and has the time to adapt then it will become unstoppable. only those with god like powers could hope to stop it.