The Silence

"All things must come to end. Once the universe is naught but proton decay, and the last life extinguishes, there will be no joy, and no more pain. No more light, and no more darkness. There will only be Silence."
-Proxima 
The Silence is a primordial concept, the antithesis to existence itself. Just as its opposite, Desire, seeks to create to fill the endless void, so too does the Silence seek to extinguish and to eliminate. An infinite number of worlds have fallen to it, and an infinite more will fall in the future. It is unstoppable. It has always existed, and it always will. 
Like all things in the multiverse, the Silence is a concept wracked with hypocrisy. Despite wanting silence, the simple fact that it wants to do so causes it to contradict itself. One other contradiction it is known for is manipulating the events on the worlds it devours. Some believe this is for fun, while others theorize that fading the light within makes these universes easier to extinguish. It does this all across the Shattered Halls, bringing about the end times through any means necessary. 
However, despite this, it is only sometimes successful. The Silence's archrival, Desire, also possesses agents. These agents, the sic'h il-dun (the worldscribers), create new worlds on its behalf, and influence outcomes within them to stave off the apocalypse. I am one of these, by the way.