You perform a spell that allows you to summon a creature you can enthrall into serving you.
The creature can be a Fae, Fiend, or Celestial. The type depends on the material used in the spell. The creature is of CR 4 or lower, of the players choice, but the exact creature is determined by the DM.
The creature makes a Charisma Save or becomes enthralled to the caster for the next minute. If the creature is summoned in the Magic circle spell, this save is at disadvantage. The creature can repeat this saving throw again at the end of a minute and if it fails three times it remains enthralled for the duration. If the creature remains for the entire duration or the spell fails after the first initial casting the caster can recast the spell causing the creature to restart the saving throws from the first throw.
Should the enthralled creature be brought to 0 hp, the creature turns to dust and returns to their original plane of existence.
* - (A gold censure bowl worth at least 1000gp and one of the following which is consumed in the ritual, A pint of fresh blood from the caster and at least 200gp worth of rare poisons (Fiend), Rare Herbs and Incense worth at least 200gp (Fae), and at least 100 gp worth of holy water and 100 gp worth of crushed silver dust (Celestial))