I think if the caster has an emotional attachment to the things invoked and the way they're invoked, it'll work much better. The only problem I could forsee is the caster knows that that world and those beings are creations of the mind. So unless the caster's a solipsist or something of the like or believes that all magic is human power and the 'entities' are just symbolic channels for that power, then most would have to convince themselves of those things' actual existence.
That being said, the language part wouldn't be problematic. It's the history/world part that would need some convincing.