Complex sentence: However, he spared Richard's nephew and designated heir, the Earl of Lincoln, and he made Margaret Plantagenet, a Yorkist heiress, Countess of Salisbury sui juris.
Split into simpler sentences: However, he spared Richard's nephew and designated heir, the Earl of Lincoln. He also created Margaret Plantagenet, a Yorkist heiress, Countess of Salisbury sui juris.