Complex sentence: This event became known as the Second Kinslaying and second Sack of Doriath, and its utterly destroyed the kingdom, though the sons of Fëanorians failed to take the Silamril, as it was saved by Dior's daughter Elwing.
Split into simpler sentences: This event became known as the Second Kinslaying and second Sack of Doriath, and it utterly destroyed the kingdom. However, the sons of Fëanorians failed to take the Silamril, as it was saved by Dior's daughter Elwing.