Murmur by WoLkAn2

Some mortals tried to worship Murmur as a god, with some even attempting to control it, but the elemental didn't care and likely didn't even notice their presence. When it yawned, they were destroyed. However, one sorcerous mortal somehow managed to survive and devised a ritual through which he and his conspirators could bring Murmur into their world using vast amounts of captured souls. Whole civilizations were brought to extinction through his soul devices, and eventually he and his allies managed to summon the creature. They used powerful containment and silencing magics—fueled by a constant supply of souls—to keep Murmur contained, but they were unable to bend it to their will and so began devising different strategies. One after another, they failed, and in the process, they weakened the rituals and accidentally gave Murmur the slightest modicum of freedom. The Codex of Blood is the only thing that survived the subsequent cataclysm that destroyed their world.