Complex sentence: Long ago, Skylands was ruled under the vicious grip by the most powerful villains called The Doom Raiders who caused havoc all over Skylands from their hideout in the Savage Badlands.
Split into simpler sentences: Long ago, Skylands was ruled under the vicious grip by the most powerful villains called The Doom Raiders. They caused havoc all over Skylands from their hideout in the Savage Badlands.