A land of death, with the corpses of gods forming the hills and mountains that make up the plane's land masses, and the rivers and oceans being formed by the blood of said gods. Blood Haven is a smaller plane/ dimension that resides in a private world outside the Brievary, and many other dimensions. It is a prison planet with limited means of accessing and houses the mental manifestation of the God.
The plane is rich in gods blood and god corpses, though one cannot utilize the corpses, the blood can serve potential purposes in the search for immortality and ascension. Be wary though, the ichor of Blood Haven comes with many drawbacks.
Not much is known about the history of Blood Haven, with its true purpose being a well-kept secret of the True Gods.
Blood Haven was a pocket realm created by Abyss and directly connected to his mind, where he would fight the manifesting depression in his mind. Eventually, this depression manifested as the 4th personality of Abyss and was able to slay Abyss's mind and take control of his body, wreaking havoc across the multiverse, and earning himself the name Iselder. Eventually, Iselder was removed from Abyss's body by the Goddess Rift and was sealed permanently in the realm of Blood Haven, with Rift severing the plane's connection to Abyss's mind.