"First of all the deathless gods who dwell on Olympos made a Golden (khryseoi) Race of mortal men who lived in the time of Kronos when he was reigning in heaven. And they lived like gods without sorrow of heart, remote and free from toil and grief: miserable age rested not on them; but with legs and arms never failing they made merry with feasting beyond the reach of all evils. When they died, it was as though they were overcome with sleep, and they had all good things; for the fruitful earth unforced bare them fruit abundantly and without stint. They dwelt in ease and peace upon their lands with many good things, rich in flocks and loved by the blessed gods. But after earth had covered this generation--they are called Pure Daimones dwelling on the earth (epikhthonioi), and are kindly, delivering from harm, and guardians of mortal men; for they roam everywhere over the earth, clothed in mist and keep watch on judgements and cruel deeds, givers of wealth [i.e. agricultural bounty]; for this royal right also they received." Hesiod, Works & Days 109 ff

Long ages before even cities existed . . . there existed in the time of Kronos, it is said, a most prosperous government and settlement . . . Well, then, tradition tells us how blissful was the life of men in that age, furnished with everything in abundance, and of spontaneous growth. And the cause thereof is said to have been this : Kronos (Saturnus, Cernunnos) was aware of the fact that no human being is capable of having irresponsible control of all human affairs without becoming filled with pride and injustice; so, pondering this fact, he then appointed as kings and rulers for our cities, not men, but beings of a race that was nobler and more divine, namely, Daimones. He acted just as we now do in the case of sheep and herds of tame animals: we do not set oxen as rulers over oxen, or goats over goats, but we, who are of a nobler race, ourselves rule over them. In like manner the god, in his love for humanity, set over us at that time the nobler race of Daimones who, with much comfort to themselves and much to us, took charge of us and furnished peace and modesty and orderliness and justice without stint, and thus made the tribes of men free from feud and happy. And even today this tale has a truth to tell, namely, that wherever a State has a mortal, and no god, for ruler, there the people have no rest from ills and toils; and it deems that we ought by every means to imitate the life of the age of Kronos, as tradition paints it." Plato, Laws 713a

For upon the bounteous earth Zeus has thrice ten thousand daimones, Watchers of mortal men, and these keep watch on judgements and deeds of wrong as they roam, clothed in mist, all over the earth." Hesiod, Works and Days, Canto III, [250]

...the Egyptians;

During the fabled "First Time, Zep Tepi, when the gods ruled in their country: they said it was a golden age during which the waters of the abyss receded, the primordial darkness was banished, and humanity, emerging into the light, was offered the gifts of civilization. They spoke also of intermediaries between gods and men - the Urshu, a category of lesser divinities whose title meant 'the Watchers'. And they preserved particularly vivid recollections of the gods themselves, puissant and beautiful beings called the Neteru who lived on earth with humankind and exercised their sovereignty from Heliopolis and other sanctuaries up and down the Nile. Some of these Neteru were male and some female but all possessed a range of supernatural powers which included the ability to appear, at will, as men or women, or as animals, birds, reptiles, trees or plants. Paradoxically, their words and deeds seem to have reflected human passions and preoccupations. Likewise, although they were portrayed as stronger and more intelligent than humans, it was believed that they could grow sick - or even die, or be killed - under certain circumstance." - Graham Hancock, Fingerprints of the Gods

"Ptah and the other gods were called, in Egyptian, Ntr - 'Guardian, Watcher'." - Zecharia Sitchin

...and the Hebrews;

"The sons of God (or children of God; 'bene elohim' and variants) are divine members of God's heavenly host...The title 'sons/children of God' is familiar from Ugaritic mythology, in which the gods collectively are the 'children of El'...The sons/children of God are also found in Phoenician and Ammonite inscriptions, referring to the pantheon of sub-ordinate deities, indicating that the term was widespread in the West Semitic religions." - Oxford Companion to the Bible

"The statement (Gen. 6:1) that the 'sons of God' married the daughters of men is explained of the fall of the angels, in Enoch, vi-xi, and codices, D, E F, and A of the Septuagint read frequently, for 'sons of God', oi aggeloi tou teou ['angels of God']. Unfortunately, codices B and C are defective in Ge., vi, but it is probably that they, too, read oi aggeloi in this passage, for they constantly so render the expression 'sons of God'; cf. Job i, 6; ii, 1; xxxviii, 7; but on the other hand, see Ps. ii, 1; lxxxviii, & (Septuagint). Philo, in commenting on the passage in his treatise 'Quod Deus sit immutabilis', i, follows the Septuagint." - Hugh Pope, The Catholic Encyclopedia

"Later Biblical books developed the idea of malochim [messengers], but it wasn't until the Book of Daniel, written in the second century BC, that some of these heavenly creatures were given names. Daniel mentions Gabriel (geber is man, El is God) and Michael. The later non-canonical books built a whole hierarchy of angels, headed by Metatron, prince of the heavenly hosts." - Harry Gersh, The Sacred Books of the Jews

"For in his days the angels of the Lord descended upon earth - those who are named The Watchers - that they should instruct the children of men, that they should do judgment and uprightness upon earth." - The Book of Jubilees

"According to the Book of Jubilees, the Watchers are the sons of god (Genesis 6) sent from heaven to instruct the children of men; they fell after they descended to earth and cohabited with the daughters of men - for which act they were condemned (so legend reports) and became fallen angels. But not all Watchers descended: those that remained are the holy Watchers, and they reside in the 5th Heaven. The evil Watchers dwell either in the 3rd Heaven or in Hell." - A Dictionary of Angels

"And I Enoch was blessing the Lord of majesty and the King of the ages, and lo! the Watchers called me -Enoch the scribe- and said to me: 'Enoch, thou scribe of righteousness, go, declare to the Watchers of the heaven who have left the high heaven, the holy eternal place, and have defiled themselves with women, and have done as the children of earth do, and have taken unto themselves wives: "Ye have wrought great destruction on the earth: And ye shall have no peace nor forgiveness of sin: and inasmuch as they delight themselves in their children, The murder of their beloved ones shall they see, and over the destruction of their children shall they lament, and shall make supplication unto eternity, but mercy and peace shall ye not attain".'" - 1 Enoch 10:3-8

"...'In the days of Jared', two hundred Watchers 'descended' on 'Ardis', the summit of Mount Hermon - a mythical location equated with the triple peak of Jebel esh Sheikh (9,200 feet), placed in the most northerly region of ancient Palestine. In Old Testament times its snowy heights had been revered as sacred by various peoples who inhabited the Holy Land; it was also the probable site of the Transfiguration of Christ when the disciples witnessed their Lord 'transfigured before them'. "On this mountain the Watchers swear an oath and bind themselves by 'mutual imprecations', apparently knowing full well the consequences their actions will have both for themselves and for humanity as a whole. It is a pact commemorated in the name given to the place of their 'fall', for in Hebrew the word Hermon, or harem, translates as 'curse'. " - Andrew Collins, From the Ashes of Angels - The Forbidden Legacy of a Fallen Race (1996) pp. 23-24

"Other Watchers stand accused of revealing to mortal kind the knowledge of more scientific arts, such as the knowledge of the clouds, or meteorology; the 'signs of the earth', presumably geodesy and geography; as well as astronomy and the 'signs', or passage, of the celestial bodies, such as the sun and moon. Shemyaza [the leader of the Watchers] is accredited with having taught men 'enchantments, and root-cuttings', a reference to the magical arts...One of their number, Penemue, taught 'the bitter and the sweet', surely a reference to the use of herbs and spices in foods, while instructing men on the use of 'ink and paper', implying that the Watchers introduced the earliest forms of writing. Far more disturbing is Kisdeja, who is said to have shown 'the children of men all the wicked smitings of spirits and demons, and the smitings of the embryo in the womb, that it may pass away'. In other words, he taught women how to abort their babies." - Andrew Collins, From the Ashes of Angels - The Forbidden Legacy of a Fallen Race (1996) p. 26

One by one the angels of heaven are appointed by God to proceed against the Watchers and their offspring the Nephilim, described as 'the bastards and the reprobates, and the children of fornication'. Azazel is bound hand and foot, and cast for eternity into the darkness of a desert referred to as Dudael. Upon him are placed 'rough and jagged rocks' and here he shall forever remain until the Day of judgment, when he will be 'cast into the fire' for his sins. For their part in the corruption of mankind, the Watchers are forced to witness the slaughter of their own children before being cast into some kind of heavenly prison, an 'abyss of fire'. Although the Watchers' leader, Shemyaza, is cast into this abyss alongside his brothers, in other versions of the story he undergoes a more dramatic punishment. Since he was tempted by a beautiful mortal maiden named Ishtahar to reveal the Explicit Name of God in exchange for the offer of carnal pleasure, he is to be tied and bound before being made to hang for all eternity between heaven and earth, head down, in the constellation of Orion." - Andrew Collins, From the Ashes of Angels - The Forbidden Legacy of a Fallen Race (1996) p. 26

"In the Day of Judgement all such spirits will be consigned to eternal torment and humanity renewed in spirit back to the generations of Adam: 'And the days will begin to grow many and increase amongst the children of men till their days draw night to a thousand years ... And there will be no old man ...For all will be as children and youths.' "The Tree of Life, fragrant and wonderful to behold will be returned to the centre ground, and the New Jerusalem will be built by God - just as later described in Revelation." - Chris King, "The Apocalyptic Tradition"

Watcher are guardian angels that (should) watch over us, the lands on the earth or the earth itself or even parts of the universe.

Then Michael and Gabriel, Suryal, and Uriel, looked down from heaven, and saw the quantity of blood which was shed on earth, and all the iniquity which was done upon it. 1Enoch 9;1

There seem to be good and bad or fallen watchers. The good ones are also called Holy ones. These are mentioned in the Bible; 

The sentence is by the decree of the watchers, the decision by the word of the holy ones, to the end that the living may know that the Most High rules the kingdom of men, and gives it to whom he will, and sets over it the lowliest of men.' Da 4:17 RSV

Their appearance is like radiant men, Ishim, shining with the Spirit of God.

Then two huge men appeared to me, the like of which I had never seen on earth. Their faces were like the shining sun; their eyes were like burning lamps; from their mouth fire was coming forth; their clothing was joyously and diverse; their wings were more glistering then gold; their hands were whiter then snow, and they stood at the head of my bed and called me by my name. 2Enoch1;4

This is ascribed to the direct proximity of God by whom they are constantly "spiritized"; inspired.

Their abode is opposite the throne of glory, and their station is facing the Holy One, blessed be he, so that the splendor of their abode resembles the splendor of the throne of glory and the brilliance of their image is as the brilliance of the Shekinah. They receive glory from the glory of the Almighty and are praised with the praise of the Shechinah. 3Enoch 28;2

Noah seemed to have looked like a child of the watchers that had descended to Earth.; 

After a time, my son Methuselah took a wife for his son Lamech. She became pregnant by him, and brought forth a child, the flesh of which was as white as snow, and red as a rose; the hair of whose head was white like wool, and long; and whose eyes were beautiful. When he opened them, he illuminated all the house, like the sun; the whole house abounded with light. 1Enoch 106;1 

The Scandinavian god Thor as portrayed in the Prose Edda also meets this description;

One king among them was called Múnón or Mennón; and he was wedded to the daughter of the High King Priam, her who was called Tróán; they had a child named Trór, whom we call Thor. He was fostered in Thrace by a certain war-duke called Lóríkus; but when he was ten winters old he took unto him the weapons of his father. He was as goodly to look upon, when he came among other men, as the ivory that is inlaid in oak; his hair was fairer than gold. Prose Edda

The Zulu know of these big athletic blue eyed reddish-blond watchers. They arrived in noisy boomerang aircrafts causing great turbulences. They were called Wazungu; whirlwind people and carried crystal spheres that allowed them to appear and disappear at will.  Sometimes a Muzungu (singular) was captured and unable to reach this sphere, he couldn't escape. 

People with blue eyes are better able to see in the dark...

In the near East area they have descended on Mount Hermon.

And God said, "And what will become of the world now without man?" Whereupon the angels replied: "We will occupy ourselves with it." Then said God: "I am well aware of it, and I know that if you inhabit the earth, the evil inclination (Yetzer ha Ra) will overpower you, and you will be more iniquitous than ever men." The angels pleaded, "Grant us but permission to dwell among men, and Thou shalt see how we will sanctify Thy Name." God yielded to their wish, saying, "Descend and sojourn among men!" Ginsberg – Legends of the Jews