Complex sentence: Dunmail met the kings in battle in the pass that divides Grasmere from Thirlmere but was defeated., he himself was killed in the fight, it is said at the hands of of Edmund himself, and his sons were subsequently blinded by the victors.
Split into simpler sentences: Dunmail met the kings in battle in the pass that divides Grasmere from Thirlmere but was defeated. Dunmail himself was killed in the fight, it is said at the hands of of Edmund himself, and his sons were subsequently blinded by the victors.