Bool, the Darkness, Goddess of Oblivion, may be drawn out of the void and imprisoned in a solid block of amber on the material plane.
Doing so is no small feat, and is extremely dangerous to mind, body, and soul.
Using salt, mark out a 20 foot wide circle. Place the 4 lanterns at equal distances around the circle, and at the center, the Godstone of the god or goddess to be sealed.
Pour the blood of an evil doer over the amber. When you are ready to summon the lord of blood, move outside of the circle and begin reading the Psalms of Terror. Progress all the way through and do not stop, lest you forfeit your soul.
If properly laid, the salt will confine The Darkness back into the Godstone, sealing any breach.
You are not safe from harm, however. Bool will use every bit of her influence on the world to stop your actions and kill you. Be on your guard, and stay in the light.
At the end of the ritual, Bool's essence will be locked away in the amber Godstone.
Ethereal chains materialize, weaving through the obsidian essence. The darkness recoils, ensnared by your mystical bonds. A captive force, harnessed by your will, held in spectral shackles of your conjuration.