A fictional entity can only be created by a human mind. Being a fictional creation, that is not based in fact, it can be given any kind of fictional capacities.
How can fictional capacities affect the real world? Just rephrasing your question, and to be clear: how can a real capacity, like the human mind, create fictional capacities, like those of Buddhism, that affect real capacities, in general.
Say gravity, derived by fact, but could be in some ways defined as fictional, as it does share some of its properties. That is not to say that the properties of gravity that affect the real world are those of fiction, but still, the properties that affect reality are those of fact. Fiction cannot turn gravity into something that it isn't.
Say I believe there is a diamond under my grandma's house, I'll mow it down to smithereens, wouldn't be the first time, she won't be surprised. Probably the only thing to be found, is that fiction affects humans. So in fictional entities, being a human capacity, its capacities over reality could be said to be those of human capacities.