User blog comment:Skeith9/Heroic Spirits Speculation/@comment-24762556-20140624072224/@comment-4572759-20140625134424

pretty much anything can be done. for stuff like nursury rhime or good witch you can put like class: Phenomenon: Caster or put Name Good Witch (phenominon). the easiest way way is to just say they realy existed. We can do anything by shaping the narrative and setting. for example summoning the manifestation of fear into beowulfs body. in this setting you summon concepts, so it is now possible to right up a sheet for the servant Fear. A good idea for summoning things like the good witch is a setting where the masters concentrate the belwifs of the public into a container and fill it with souls/energy from the source how much goes into the servant is restricted by the magus and the public beleifs of the servant.

so as a rule of thumb as long as your not to goofy it can probally be a servant, just be creative with the setting.