Considering that there were many deities being worshipped and its most likely that the general populous prayed for decent/reasonable (non "evil") stuff, then it's probably safe to assume that most people worshipped the more philanthropic, benevolent, and optimistic "good" gods over someone like Hades. Given that assumption, how did Christian missionaries react and handle their beliefs; both directly and personally in their writing or theology.
Its fairly common knowledge now that the 25th of December (on the Gregorian Calendar) is a proxy for some benevolent Solar deity's holiday as there's no real definitive record of which date Christ was born. Considering that maybe some of the teachings were the same, how did Missionaries approach these congruences between Pagan and Christian teaching?
The larger problem was that the pre-Christians of Europe had a difficult time with dividing the world into strictly good and evil halves. Supernatural entities were dangerous because they were powerful and so they had to be treated with respect and caution, but nearly all of them were capable of being helpful under the right circumstance. The following excerpt is from my draft Introduction to Folklore (which I will be e-publishing in September). This excerpt begins after a discussion of Frau Welt -Dame World - as opposed to Frau Walt - the forest woman - and it moves on to the world of elves, but these are analogous to more powerful supernatural beings that either should or should not be called gods. "God" is a problematic term when modern monotheists use it to understand pagan religion since it elevates pagan supernatural beings to something that is similar to the Christian god. Here's the excerpt:
The most important contrasting aspect between the two supernatural beings reflected the fact that the peasantry was out of touch with the idea that the world could be divided into good and evil. This concept came from the Middle East with the Bible, which acquired it from ancient Persia. The fact that Dame World is evil, whereas the forest sprite is simply dangerous, reflects the conservatism of the peasants. The dualism of good and evil, which was the property of the educated of medieval Europe, was too foreign to the peasants of Northern Europe – or even for the lower clergy – and so they reacted to it without enthusiasm. This constituted a major obstacle to the long process of Christianization of the peasantry. For the minnesingers, in touch with the more exotic, educated foundations of their religion, it must have seemed rather obvious that the forest sprite, or her medieval German equivalent, was a perfect symbol for the world, enticing and yet fundamentally corrupt and evil as Christian theology viewed the world. This sort of symbolism would no doubt have been lost on the peasantry.
It is common to view European civilization as a synthesis of Classical and Christian worlds with “barbaric” elements thrown in for flavor. Both the peasantry and the learned repeatedly strove to blend the diverse and often conflicting portions of their complicated heritage. Yet the synthesis, as far as the assimilation of the abstractions of good and evil is concerned, was never really achieved before the Industrial Revolution in Northern Europe. A few examples from both medieval and pre-industrial popular culture suffice to demonstrate this.
One of the pressing problems for the European peasant was how to account for the world’s various supernatural beings, entities not mentioned in Christian documents. The folk constantly faced the question of how these creatures fit into the system of the saved and the damned. Educated priests told people, after all, that the strict division between good and evil had universal application. How, then, did the elves and fairies rank in the Divine plan? The peasant was never sure how to answer this question. The educated elite, on the other hand, had no trouble with this problem: since elves and fairies were not mentioned in the Bible as affiliated with God, they were, consequently, evil. This is the position that the Beowulf-poet took in the ninth century when he suggested that elves, like the monster Grendel, descended from Cain.
From him the evil brood were all born,
Giants and elves and evil spirits,
And also the giants who fought against God
For a long time; He paid them retribution for that.
This sort of interpretation, however, never caught on with the peasantry although it was acceptable to the higher clergy. Many people were condemned as witches for innocently making sacrifices to elves and similar supernatural beings.
Pre-industrial European legends show that peasants until recently thought of elves and fairies as neutral beings, without a definite place in God’s spiritually-dichotomized world. Some legends explain that the elves and fairies were angels who refused to take either side in the great conflict between God and Satan. Other legends suggest these supernatural beings were the souls of pre-Christian people, or that they were the deceased who were not good enough for heaven, but not bad enough for hell.
When the peasants did take a stand concerning the position of elves and fairies in relation to God, they generally said that the entities have at least a chance for salvation. Christiansen classifies the stories along this line as Migratory Legend 5050, “The Fairies’ Prospect of Salvation.” In this legend, someone hears the fairies singing in their mound, and he tells them that they should not be so happy because they have no more chance for salvation than his cane does of sprouting leaves. At this, the music stops, and the fairies begin to weep. When the man awakens the next morning, he finds that his cane has sprouted leaves, and so he hurries back to the mound to tell the fairies that God has sent a sign that they do indeed have the ability to attain salvation. Upon hearing this, the fairies resume their music.
This popular legend shows clearly that if pressed to make a definite judgment, peasants said that the fairies are like men: they are neither good nor evil as a whole, and they can attain salvation. The peasants retained a belief in the neutrality of the fairies and at the same time worked them into the Christian cosmology. Here, the synthesis of the Christian concept of good and evil has been tenuously reached. Variants of the legend even incorporate the Biblical motif of the sprouting cane, a sign that told the Jews that the house of Levi was to be the house of priests. The ultimate failure of the peasants’ attempt to find a synthesis between the concepts of good and evil and their belief in fairies is indicated by two factors. First, the educated elite of Europe and the higher clergy never accepted this judgment, and second, other legends of the peasantry continued to place the fairies in an ambiguous position in relation to good and evil. In fact, still other legends tell of the fairies’ fear of crosses and holy words.
The example of the fairy shows how difficult it was for European peasants to place one of their neutral, pre-Christian beliefs into the Christian universe. The treatment of the devil in European folklore illustrates the obstacle peasants faced when assimilating even the most absolute symbol of evil into their belief system. The devil usually appears in the place of the stupid ogre or in the role of a trickster. Although these beings are often the opponents of humanity, and they are certainly dangerous, they are also rather amusing and can be beaten. Peasants clearly understood that the devil wishes to gain human souls, but they could not help thinking of the devil as just one of many perilous supernatural beings in the world. The pre-industrial folklore of Europe shows the devil as an easily-defeated, sometimes rather pathetic creature who was not as absolutely evil as Christian dogma taught.