The Far Realm is an alien realm outside the known Multiverse, outside Time itself. Before the beginning of Time and after its end, the Far Realm can be found.
Occasionally, when the stars and planes are in a certain alignment, doorways or rifts can open between the Far Realm and ordinary reality, allowing horrors to pour out. The natives of the Far Realm are incomprehensible and maddening to eyes accustomed to the three dimensions and linear causality of the realms we know. Their motives are unguessable, at once simpler and more complex than mere hunger.
The Far Realm has no inherent alignment that can be recognized. It is neither chaotic nor lawful, neither evil nor good.
The Far Realm is toxic to ordinary reality. Perhaps, to some extent, the reverse is true as well.