Masalisk

The creature that would become known as Masalisk of the Pact of Iron did not begin as a monster. It did not even begin as sentient. A pair of warring Ascendant deities, both of whom's names are lost to time, were dragged by their conflict to the material realm, where the final duel took place. As one god slew the other, the land was devistated, leaving behind a massive pit, hundreds of miles across, referred to as the "Maw". But, in the depths of the Maw, fragments of the slain deity remained. In that pit, they were found by a small colony of spiders, which began to feed on the divine flesh. As they did, they grew in size, power, and intellegence, but along with it, a hunger that could not be sated. The spiders fell on one another, consuming eachother for the fragments of divinity within them, until one single spider, now over twenty feet tall, remained. This creature became known as Masalisk, and the pit became known as the Maw of Masalisk. Masalisk began hunting, turning the entire region into it's hunting grounds, seeking to sate the endless hugner that could never be satisfied by mortal flesh.
When the Order of the Golden Rose came for Masalisk, armies flung themselves at the beast, eventually wearing it down with sheer numbers, as the body was torn apart and burned down to the last.