Sentence:  The chief exploit of the hero, Beowulf the Great, is the destruction of the two monsters Grendel and his mother; both like most of the evil beings in the old times, dwellers in the fens and the waters; and both, moreover, as some Christian bard has taken care to inform us, of "Cain's kin," as were also the eotens, and the elves, and the <WSD>orcs</WSD> (eótenas, and ylfe, and orcneas). 
Meaning of the word marked with <WSD> tags:  A mythical evil monstrous humanoid creature, usually quite aggressive and often green. (from 17th c.)