If anyone is interested there are some alternative rules for Stormbringer fifth edition that allow a sorceror to summon creatures from another plane that aren't generally classed as demons that could be used for Magic world, if you want that sort of summoning to be part of your games. "The summoning skill is a useful measure of the general magic proficiency of a character and can be used in a simple way to deal with the summoning of creatures that are predefined as coming from another plane, such as the Creatures of Matik, the Elenoin, the Steeds of Nirhain, or even a Vadagh from Corum's world, an Eldren from the ghost-worlds of Erekose's Earth, or a traveller of the spheres like Wheldrake the poet." http://www.stormbringerrpg.com/docs/Alternate Magic.pdf