The hardest part about writing a fantasy story isn't the actual writing, but the generation of ideas and plot points. Everything has to link together and be interesting enough that it grabs the readers attentions throughout the entire book.

All to often, a great idea fizzles in the long run. I guess that's why they created short stories. If you find yourself adrift in a sea of hopelessness, then why not look at at the legends and mythologies of ages past. They have spent literally hundreds of years crafting and perfecting these characters and ideas, so why not take advantage.

Percy Jackson was almost completely based on Greek mythology, The Matrix used the beliefs of Buddhism and Hindu and even Damien was based on Christian ideology. Writers and filmmakers have been cannibalizing from the ancients for centuries. Even Shakespeare brought out a few in Midsummer Nights Dream.

Do you need a great villian? Why not make a mix of Hades and Eres to create something powerful and power hungry. Do you need someone to act as a creative influence, then why not borrow from the muse...literally.

You may want to create something that is completely original and free of influence, but anyone that has been writing for very long knows there is no such thing. Everything has an influence and its best to just admit that from the start and use it. Fantasy is about bringing worlds to life and people have been doing that since time immemorial.