Complex sentence: Upon his awakening at some time after the creation of the Elves in, he travelled great lengths to the places where the other Fathers of the Dwarves had awoken before eventually arriving at the Mirrormere, a lake in a valley at the feet of the Misty Mountains.
Split into simpler sentences: Upon his awakening at some time after the creation of the Elves in, he travelled great lengths to the places where the other Fathers had awoken before. He arrived at the Mirrormere, a lake in a valley at the feet of the Misty Mountains.