Upon speaking foul words, the spell conjured a demon of the caster's choice, among several options that included barlgura, shadow demon, babau, dybbuk, bulezau, rutterkin, and other demons of similar or lesser strength. As the caster grew in power and experience, it became possible to summon even stronger demons.
The demon appeared at a visible location of the caster's choice within a range of 60 feet (18 meters). It obeyed the caster's verbal commands, but constantly attempted to resist them. If the caster knew the demon's true name, it became considerably easier to control. In the absence of any commands, the demon only attacked in self-defense. If the caster's control over the demon ended before the spell expired, it entered a rampage, pursuing and attacking every creature in sight that was not a demon, including the caster, starting with the ones that were closest to it. The caster could form a protective circle large enough to surround one human-sized creature, using up the blood that was required to cast the spell. The summoned demon could not cross the circle or harm anyone inside it.
The demon remained summoned for up to one hour, as long as the caster kept concentrating, or until it was killed. It immediately disappeared when killed or when the spell reached its full duration. However, if the caster broke concentration early, an uncontrolled demon remained for several seconds before returning to the Abyss, while a demon still in thrall was dismissed immediately.
The spell required verbal, somatic, and material components. The material required was blood from a humanoid killed within 24 hours of the casting of the spell. The blood could not be reused as a component if used to draw the protective magic circle.
- Jeremy Crawford, Mike Mearls, Robert J. Schwalb, Adam Lee, Christopher Perkins, Matt Sernett (November 2017). Xanathar's Guide to Everything. Edited by Kim Mohan. (Wizards of the Coast), pp. 148–149, 166–167. ISBN 978-0-7869-6612-7.
- Ossian Studios (August 2019). Designed by Luke Scull. Neverwinter Nights: Tyrants of the Moonsea. Beamdog.
- Mike Mearls, Jeremy Crawford, Christopher Perkins, James Wyatt (2014). Dungeon Master's Guide 5th edition. (Wizards of the Coast), pp. 306–308. ISBN 978-0786965622.
- Mike Mearls, et al. (November 2016). Volo's Guide to Monsters. Edited by Jeremy Crawford, et al. (Wizards of the Coast), pp. 221–222. ISBN 978-0786966011.
- Mike Mearls, Jeremy Crawford (May 29, 2018). Mordenkainen's Tome of Foes. Edited by Kim Mohan, Michele Carter. (Wizards of the Coast), p. 254. ISBN 978-0786966240.