Formless Mother
The Formless Mother, also called the Mother of Truth, is an Outer God. She has no body you can see, and you never fight her. Mohg came upon her far below the surface, and his power comes from her.
She hungers for wounds and grants strength to cursed blood. Her presence is felt through the bloodflame weapons and incantations tied to Mohg.
Lore
Piercing the Formless Mother with Mohgwyn’s Sacred Spear coats the weapon in bloodflame, and the Bloodboon incantation works by thrusting an arm into her to spray bloodflame across the ground. She is said to be everywhere at once, so a ritual spear can reach her from any spot in the Lands Between.
The Mother of Truth also promised salvation to the people of Prospect Town, and turned them into bloodfiends.
Many players believe the Land of Reeds fell under her sway, given its warriors’ blood-soaked madness and their love of weapons that cause blood loss. The game hints at this but never says it outright.