The most famous monster in Old English poetry must be Grendel, the man-eating enemy in the poem Beowulf. The poem mainly refers to Grendel by name as an individual. Grendel is also called an 'eoten', e.g. at the climax of the fight with Beowulf Grendel is struggling to break loose from Beowulf's grip:
The monster strained away
--Beowulf, line 761, translated by Michael Alexander
Eoten was utweard
--Beowulf, line 761
Eotens in general are also referred to in the poem, sometimes in association with 'cyn', meaning something like tribe or kindred:
--Beowulf, line 112
--Beowulf, line 421
--Beowulf, line 884
So eotens were a particular type - the modern term might be something like species - of monster, and Grendel could be described as an eoten. What sort of creatures were eotens thought to be?
From Cain came down all kinds misbegotten
- ogres and elves and evil shades -
as also the Giants, who joined in long
wars with God.
--Beowulf, lines 111-114, translated by Michael Alexander
eotenas ond ylfe ond orcneas,
--Beowulf, line 112-113
In this list of monsters 'eotenas' (here translated as 'ogres') are considered by the Beowulf poet to be descendants of Cain, the first murderer. They are clearly seen as one among several types of evil creatures - "all kinds misbegotten".
The fell and fen his fastness was
The march his haunt
--Beowulf, lines 102-103
. walked nightlong
The misty moorland
--Beowulf, lines 161-162
up steep screes, by scant tracks
Where only one might walk, by wall-faced cliffs,
Through haunted fens - uninhabitable country
--Beowulf, lines 1410-1411
So Grendel (and presumably other eotens) lived in wilderness and wasteland, including mountains (fells), moorlands and marshes or fens. The kind of country where humans cannot, or at any rate do not, live.
Grendel's particular home is in an underground cave reached by swimming down through a mountain lake in a swallow hole:
Mysterious is the region
They live in - of wolf-fells, wind-picked moors
And treacherous fen-paths: a torrent of water
Pours down dark cliffs and plunges into the earth
An underground flood
--Beowulf line 1357-1361
Grendel and his mother are described in Beowulf:
Of huge wayfarers haunting the moors,
Otherworldly ones: and one of them,
So far as they might make it out,
Was in woman's shape: but the shape of a man,
Though twisted, trod also the tracks of exile -
Save that he was more huge than any human being
--Beowulf, lines 1347-1353
There's no more detailed description in the poem, but this shows clearly that eotens were considered to be approximately humanoid in form but larger than a human.
Beowulf's wrestling matches with Grendel and then with Grendel's mother show that eotens were considered to be immensely strong.
Both Grendel and Grendel's mother only ever come to Heorot by night. During the day they lie up in the cave under the lake. So eotens were nocturnal.*
The eotens' diet consists of human flesh in prodigious quantities, as the Beowulf poet describes in grisly detail:
Grim and greedy, he grasped on their pallets
Thirty warriors, and away he was out of there,
Thrilled with his catch
.He set his hands on
A sleeping soldier, savagely tore at him,
Gnashed at his bone-joints, bolted huge gobbets,
Sucked at his veins, and had soon eaten
All of the dead man, even down to his
Hands and feet
There is no indication that eotens are superior to humans in cunning, intellect, technology or magic. Grendel and Grendel's mother do not lay traps or cast spells, they just grab people and eat them. They are formidable because their physical strength is superior to that of the average human warrior. Beowulf is possessed of superhuman strength and overcomes them by physical might, aided by a sword in the case of Grendel's mother.
This gives a fairly clear picture of eotens - assuming that Grendel and Grendel's mother are typical of the species - as large, strong, malevolent, nocturnal, roughly humanoid creatures that live in wastelands and like to eat human flesh. They do not appear to make use of technology or magic, nor are they shown as cunning or devious. I don't think we can tell whether they are thought of as stupid compared with humans, because neither Grendel nor Beowulf tries to outwit the other.
So, what word to use for these creatures (or, more precisely, characters' beliefs about these creatures) in fiction? I could use the Old English word 'eoten' from the Beowulf poem. However, it is no longer in common use in modern English, so not many modern readers are likely to recognise it. I could modernise the spelling to something like 'ettin' or 'etten', as Tolkien did in Lord of the Rings (" .the Ettenmoors, the troll-fells north of Rivendell ", as Aragorn says in Book I Ch. 12). But that's not much more recognisable to a modern reader, except perhaps to Tolkien geeks. The Oxford English Dictionary categorises 'ettin, eten, eoten' as obsolete, so the word can't even be looked up easily unless one has access to a specialist dictionary.
'Eoten' is cognate with the Old Norse 'jotun', which occurs frequently in the Norse legends and is usually translated into modern English as 'giant'. However, the Beowulf poet seems to have thought of 'eotens' as somehow different from the creatures called by the Latin-derived name 'gigantas', since they are given separately in the same list. That could just be elegant variation to fit the metre, or it could indicate that they were considered different types of monster. Another objection is that the Norse jotuns appear to have been thought of as a group of creatures on a par with the gods. In the stories in the Prose Edda, the jotuns fought with the gods, intermarried with the gods, and lived in a world that was either not part of the human world or was separated from it by a major barrier (see article on the Old English and Norse worlds). The Beowulf poet may have been familiar with this sort of concept, since the 'gigantas' are described as having fought against God. Eotens, on the other had, seem to be a much more earthbound sort of creature, living in unpleasant corners of the same world that humans live in. Grendel's lair is less than a day's ride from Heorot, with no major obstacle in the way. So eotens seem to be a sort of step down the supernatural hierarchy from giants.
Grendel is referred to once in Beowulf as 'thyrse', line 426. The Old English word 'thyrse' or 'thurse' is obsolete in modern English but occasionally appears in place names, e.g. Thirlspot in Cumbria. It's usually translated as 'giant' or 'demon'. Michael Alexander translates 'thyrse' as 'troll' in Beowulf for the alliteration - "a trial against this troll". I could use 'thyrse' or a modernised version thereof, but that's no more easily recognisable than 'eoten'.
I could use 'ogre', as Michael Alexander occasionally does in his translation. However, I don't personally like the word, partly because it conjures up a more fearsome image than I had in mind and partly because it doesn't have a particularly Old English or Norse feel about it. 'Ogre' doesn't appear to be directly derived from the Old English 'orcneas', by the way - the Oxford English Dictionary says its derivation is from Old French in the late twelfth or thirteenth century, and gives its first recorded use in English as 1713, in a translation of The Arabian Nights. I suppose 'orcneas' could have lain dormant for several centuries and resurfaced as 'ogre' in 1713 without any recorded trace in the intervening period, but this seems rather unlikely.
In the end I settled on the Scandinavian word 'troll'. 'Troll' occasionally appears in place names in areas in Britain with a strong Norse influence, such as Trollers Gill in Yorkshire (Yorkshire was part of the ninth-century Danelaw and later part of the Anglo-Norse kingdom of York), and especially in northern and western Scotland, such as Trollaval on the island of Rum, and Trolla Vatn in Orkney (a name that could have come straight off a modern Norwegian map; it translates as 'troll water' or 'troll lake'). The 'Troll' place names presumably came to Britain with the Norse incursions in the ninth century or so. If cultural links with Scandinavia were also strong in earlier centuries there may be a possibility that 'troll' could have been present as a regional dialect word in some regions prior to the ninth century, but there is no evidence for this. The Oxford English Dictionary has no record of 'troll' in use in English, except as the regional dialect word 'trow' in Orkney and Shetland, until it was (re?)adopted into modern English from Scandinavia in the middle of the nineteenth century. Because of this (re)introduction, 'troll' is in use in modern English and is reasonably familiar to a modern reader, if only from the Tale of the Three Billy Goats Gruff, Terry Pratchett, or from Tolkien via Peter Jackson's films.
'Troll' has roughly the right image to do duty as a translation for Old English 'eoten': large, strong, malevolent, roughly humanoid, not conspicuously bright or devious, wilderness-dwelling, nocturnal creatures who eat human flesh. The modern image of trolls perhaps has a more specifically mountainous or rocky association than the eotens in Beowulf, which may be partly derived from Tolkien's tale in The Hobbit of three trolls turned to stone by sunlight (a fate that befell a dwarf in the Poetic Edda*). That happens to fit quite well in the context of Paths of Exile, much of which is set on the moorland of the Peak District where the strange rock formations play on the beliefs held by some of the characters (see Locations: Derbyshire's gritstone tors for pictures).
*There's no indication in Beowulf that Grendel or Grendel's mother would have turned to stone if exposed to sunlight. A story on those lines is told about a dwarf called Alvis in the Poetic Edda who was tricked by Thor into talking until sunrise and then turned to stone. That story may have been what Tolkien had in mind when he created the scene in The Hobbit of the three trolls turned to stone while they were arguing over the best way to cook thirteen dwarves and one hobbit. (Note that Tolkien's dwarves don't have a problem with sunlight.)
Beowulf Old English text, available online.
Beowulf, translated by Michael Alexander. Penguin Classics, 1973, ISBN 0-14-044268-5.
Poetic Edda, Alvissmal, available online.