Here's an eldritch Lovecraftian entity called The Root of All Evil, the entity who gave Bill Cipher his powers.
This entity is far more older than the Calamity Guardian and the Axolotl, and he’s a lot more malevolent and chaotic than Bill Cipher ever was, as this creature wants to assimilate the entire multiverse into chaos and destruction, causing the Axolotl to imprison him for eons. In some point in the past, he encounters Bill in his home dimension, who was bored of his home's rules of gravity and The Root of All Evil gave Bill the chance to challenge the rules of his hometown, causing Bill to destroy the 2nd Dimension entirely.
The Root of All Evil is based on The One Below All from Marvel, Invictus from Final Space, the Mind Flayer from Stranger Things, Adam from Neon Genesis Evangelion and Nyarlathotep from the Lovecraft Mythos.
