Another short Fitt. Hrothgar mourns the loss of Aeschere, taken by Grendel's mother. He then tells of the wilderness where Grendel and his mother had lived. The details are not completely consistent, but they inspire fear, if not awe. The Haunted Mere in Beowulf by William Witherle Lawrence (available on Archive.org here) discusses this section in detail. Immediately after, Hrothgar turns to the matter at hand: the social and legal necessity of revenge, and asks Beowulf to take on the work.
XXI. GRIEF FOR ÆSCHERE
Then Hrothgar spoke, the helmet of Scyldings.
“Say nothing of peace! Pain is renewed
“for every Dane. Aeschere is dead,
“an older brother to Yrmenlaf,
“my rune reader, my ready counsel,
“my right-hand man in many fights,
“who warded my head from warriors’ blows
“and crushed boar-crests, a credit to mankind.
“Aeschere was always worthy.
“He found in Heort a hand to slay him 1330
“an elusive killer. I cannot tell
“if, proud of her prey, she pressed on home
“full-bellied from her feast. The feud she avenged
“was last night’s fight when you felled Grendel,
“wrenched him round in a rough embrace
“because too long my countrymen were
“weakened and wasted. War finished him.
“His life ended. Another has come,
“a strong evildoer, to strike in return
“and has gone far towards her feud’s success, 1340
“as many thanes might be thinking
“who weep in their hearts for the wealth giver.
“A hard grief to bear! The hand has now fallen
“that offered aid to everyone’s hopes.
“From local landsmen, my loyal subjects,
“and high counsellors I heard stories
“that they have seen such a couple
“haunting the wetlands, huge distant walkers,
“unearthly beings. Out of them, one—
“for they could tell the truth of this— 1350
“seemed a woman. The second, though grotesque,
“in man’s form traced murderers’ trackways,
“but more massive than men ever are.
“The country folk call him Grendel.
“They never knew the name of his father
“nor if others were ever born,
“Their little-known country
“has wolves on its hill-slopes, windy headlands,
“a fearsome fen-path. A flowing stream there
“descends to fill, under foggy cliffs, 1360
“a lake under ground. It is no great distance,
“as measured in miles, that the mere stands.
“Ice-covered groves grow up to its edge.
“The sure-rooted trees shadow the water.
“There, nightly, one sees a sight against nature:
“the water burns. No wise man living,
“no son of man, has sounded that mere.
“Though a heath-stepper with hounds pursuing,
“a firm-antlered hart, flees a great distance
“in a long chase, he chooses to lose 1370
“his life on land than leap in the water
“to hide his head. No happy place.
“There, a whirlpool whips the waters high,
“black up to the clouds when blasts are stirring—
“evil weathers—till the air darkens
“and heaven weeps.
“Now help, once more,
“is in your hands. You have not seen
“the fearful country you could find her in,
“that sinful being. Seek if you dare,
“and I will reward you with wealth for this fight, 1380
“ancient treasures, as I earlier did;
“if you return, with twisted gold.”