...

[He shifted uncomfortably, taking his sunglasses from where they were sitting on his head and sliding them back into place over his eyes.]

Honestly, I didn't study in the department for a particularly long time, so it's not as if I have the kind of knowledge someone like a necromancer might. But it all depends on the strength of what you're trying to summon. Simplistic spiritual familiars and other minor things can be manifested without a great deal of difficulty or effort.