Finnbheara was originally one of the Tuatha De Danann, he is mentioned as such in the Agallamh na Seanoach and is also said to be a brother to Oengus mac ind Óg and youngest son of the Dagda according to the Altram Tige Dá Medar. His mother is not mentioned. In the altram Tige Dá Medar he is called Finnbarr Meadha and he and Oengus get into a violent disagreement after he disparages one of Oengus's foster daughters while visiting Oengus's home. He is also sometimes said to be a rival of Donn Firinne, another Fairy King, although O hOgain suggests that the two could represent complementary rulers of the year in much the same way other scholars have suggested Áine and Grianne represent the summer and winter suns.
He is generally described as a handsome man, sometimes said to dress in black (Briggs, 1976). We can perhaps assume from his name that he is fair haired. In one story he appears in a coach drawn by four white horses and in another he is riding a black horse (Briggs, 1976). Finnbheara has a strong association with horses in general and with horse racing in specific, and in one tale he appeared to aid Lord Hackett by acting as jockey to his horse in a race before disappearing (O hOgain, 2006).
Finnbheara is married to the Fairy queen Una but he has a reputation for his love of mortal women, and women in general. In the aforementioned Altram Tige Dá Medar he had traveled to visit his brother in order to see Oengus's foster daughters, who had a reputation among the Tuatha De for their beauty and manners. In a story from folklore he abducts a woman named Eithne and keeps her for a year until her husband successfully wins her back from him by digging into Finnbheara's sidhe, salting the earth there, and freeing her from the enchantment she was under by removing a piece of fairy clothing she was wearing (MacKillop, 1998). In the Feis Tighe Chonain he appears as an Otherworldly rival competing with Finn mac Cumhal over a woman (O hOgain, 2006). In many other anecdotal tales he was known as a womanizer and for taking mortal women into his sidhe, even though his own wife was said to be peerlessly beautiful.
A mercurial figure, Finnbheara is well known for abducting people but also for blessing those he favors. He heals a sick woman in exchange for food, and is known for rewarding any blacksmith brave enough to try to shoe his three legged horse (MacKillop, 1998). He is known to appear to mortals and offer them aid of various kinds, but especially aid in horse racing, and then sometimes to invite them into his sidhe. These invitations may be a trap but on other occasions the person would be his guest at a feast, often finding the other guests to be dead people they had known previously, and would return safely to mortal earth the next day (Briggs, 2006). The success of crops in Connacht are also thought in folk belief to rest on both Finnbheara's presence in the area and his favor. In some folklore the crops bloom when Finnbheara and his fairies win at hurling against the fairies of rival provinces (O hOgain, 2006). In one anecdotal tale the fairies of Ulster challenged the fairies of Connacht and the two met and fought as clouds in the sky and "it was thought that Finnbheara won because there were good crops in Connacht that year." (MacNeill, 1962, page 593). It was generally believed that there was a standing rivalry between the Good People of Ulster and Finnbheara's people.
Finnbheara is an interesting figure in folklore and one who has a more complex history than is sometimes appreciated in fairylore. A member of the Tuatha De Danann and also a Fairy King, possibly also ruler of the dead, known to abduct mortals but also to aid them for little or even no recompense. He bridges the space between mythology and folklore, found in myths from the 12th century and also in modern day folklore around Cnoc Meadha. Those who seek to better understand the way that the Tuatha De Danann have merged with and affected our understanding of fairies can learn a lot by studying Finnbheara's stories.
*the relationship between the fairies and the dead is complicated but we also see this sort of crossover with Donn Firinne, who is called both a Fairy King and a god of the dead.
MacKillop, J., (1998) Dictionary of Celtic Mythology
Altram Tige Dá Medar http://www.maryjones.us/ctexts/fosterage.html
O hOgain, D., (2006) The Lore of Ireland
Briggs, K., (1976) A Dictionary of Fairies
MacNeil. M., (1962) Festival of Lughnasa