Complex sentence: Also, Nenya, one of the Three Rings of Power, was described as the Ring of Adamant, once again the Dark Tower Barad-dûr is described as being a tower of adamant crowned with iron.
Split into simpler sentences: Also, Nenya, one of the Three Rings of Power, was described as the Ring of Adamant. Whats more the Dark Tower Barad-Dur is described as being a tower of adamant crowned with iron.