Rateliff maintains that Sauron first appears in the Tolkien legendarium as Sauron the Necromancer in the poem, The Lay of Leithian, and after the destruction of the tower at Tol Sirion, the Necromancer fled to Taur-na-Fuin, which he thought to be Mirkwood.
Here again, live action merges seamlessly with digital artistry -- human horsemen by the thousands riding against swarms of Sauron's orcs, whose ranks are augmented by mountainous, mastodonish creatures called Mumakil, plus Fellbeast dragons that swoop down on their prey like Stuka bombers.