The Tome of Want is an accessory in your inventory.

Select a Scripture in the Ritual Rites section of the Tome of Want to influence the weapons, armor, and materials that you will receive.

Activate the Tome of Want by infusing it with Essence of Desire.

Acquire Essence of Desire when depositing the Dreadnaught's Metastasized Essentia at the Taken Altar in the Last City.