At the time of posting, this was the 2015th question posted on Puzzling Stack Exchange, in the year 2015.
Take the number of multiples of 5 among the numbers featured in this puzzle.
Multiply it by the number of types of creature beyond red twisted ter'angreal doorways.
Subtract the figure you now have from the number of Scheherezade's tale narrated by Poe.
Divide by the number of children fathered by Sidorio.
Add the number of entries in each Classic FM Hall of Fame.
Subtract the product of the number of siblings of Frodo Baggins's mother and the number of legitimate children fathered by Walder Frey.
Add the number of days from now (the date of posting, 3 April) until the Easter Day celebrations in Romania.
Subtract the number of Sitters in the "Hall of the Tower" in Salidar.
Add the number of stars on the banner of Gondor.
Subtract the number of elements named after Ytterby.
Subtract the figure you now have from the user ID of the most prolific question-poster on Puzzling.SE.
Add the number of primes greater than 10 among the numbers featured in this puzzle.
What is the number you now have?
Information from comments on answers:
the SciFi & Fantasy crowd (alexwlchan and Michael Edenfield) have got all but one of the numbers they need. You just need to correct their answers in a single place and you'll get the right solution.
apparently neither of them has read as far as Immortal War.