Complex sentence: He is an earl who was ousted from his earldom by his nephew the Yder the Knight of the "Sparrow-Hawk", who was compelled to restore his land when bested by Geraint.
Split into simpler sentences: He is an earl who was ousted from his earldom by his nephew Yder the "Knight of the Sparrow-Hawk". Yder is compelled to restore his land when bested by Geraint.