A friend of mine was having some trouble finding any good sources on Celtic magical traditions that weren’t tainted by Wiccan influence. So, I did some digging and this is what I came up with! This will just be a very brief run down on Celtic history, religion and magical traditions. It is *brief* meaning that it is in no way all inclusive and focuses mostly in ‘Irish’ Celtic traditions because I couldn’t find much information on other strains of Celtic beliefs in my research. Click the bolded topic links to take you to more detailed articles with sources!
The Celts were a large group of people that colonized much of Europe during the Bronze Age. It is said that they did not take land by force, but instead peacefully assimilated the preexisting cultures into their own. How true this statement is could definitely be up for debate, but if there was any violence used in the conquering of their territories, the indigenous peoples did not survive to tell of it. The Celtic Empire was said to have originated in Austria or somewhere in Central Europe and by 450 BC it had expanded to France, the Gauls, the British Isles, Poland, Bohemia, the Iberian Peninsula, Northern Italy and even parts of modern day Turkey. The Celtic people were said to be a peaceful, nature-revering society that focused on poetry and art. When the Roman empire began to expand more the Celtic Empire was pushed back and restricted to mostly the British Isles. There are several people who claim to have Celtic ancestry that are alive today, but similar to how some Modern day Egyptians claim to be descended from Ancient Egyptians, it is just very hard to prove since there has been so much movement and intermingling of genealogy in Europe.
The Celt’s religious practice was called Druidism and their priests were known as Druids. They taught peace and harmony through coexisting with nature. Tradition and folklore speaks of a ‘Land of the Young’ which is an otherworld/underworld sometimes thought of as a different plane of existence, sometimes thought to be a separate island that you could actually sail to. In the Land of the Young there was no sickness, no death, no unhappiness and no old age. It is said that one day in the Land was equivalent to a hundred years on this plane. Celtic mythology is extensive and while I did do a post of basic (keyword here is BASIC) description of Celtic deities, a more detailed account of each individual story and legend can be found here. The Celts practiced a polytheistic religion, that is to say that they worshiped many different gods. For a basic list of Celtic deities, check out this post!
Celtic Festivals have since been adopted and altered by Christianity and Wiccan belief systems (Not to say that their holidays are invalid in anyway, I’m just saying that they’ve gotten a bit off track from what the original festivals were, originally). Samhain was their new year. How it is pronounced is a matter of great debate because of the many, many different dialects of Gaelic, but what we do know is that it is definitely not sam-hayn. Hah. Samhain was a pretty big deal, socially and culturally, and was a harvest festival as well as a new year celebration. After Samhain comes Yule, the celebration of the Winter Solstice. For both Samhain and Yule, new beginnings and growth were important themes. Beltane is celebrated in May and is the festival celebrating the beginning of summer and the end of spring. Fertility was a big theme during Beltane and their Midsummer celebration, called Litha by some. The last holiday, and perhaps one of the most important, is Lugnasad, or as it would later be known, Lammas. It came halfway through Samhain and Beltane. Ludnasad was a time of thanks and usually a big feast was held. There is evidence to suggest that the Celts (or at least the Celts who live in the Gauls) performed human and animal sacrifice for certain festivals and celebrations as a form of worship to specific deities. Please note that the names of the holidays/which holidays were celebrated may have differed depending on the particular sect of Celtic cultures that practiced them.
Celtic magical tradition was usually reserved just for priests. There are many different specific practices in the Celtic tradition, but as I said before, its hard to discern between what is original and what is the Wiccan version. There are a few practices I do know about that I can discuss, however. First, Saining. This is the Celtic tradition with roots in Scottish and Irish cultures that is the blessing or consecration of an item. The process of Saining involves the use of blessed water, the burning of juniper, and spoken prayers or poetry. Another practice that is widely known is Ogham, or Tree Lore. The Ogham is an alphabet usually carved on stones or pieces of wood. Ogham are often used for divination, and each tree has a special meaning and represents a number, as well as certain events and signs. Druid priests who focus on Tree Lore are called Ovates. Ovates learn to not only work with the Ogham and other elements in nature, but also learn to harness the Nwyfre (the Life Force) and tame the Anam (the soul). In the Celtic magical system there were three main focuses: Draiocht (Magic), Taghairm (Divination) and Corrguine (Herbalism). A common practice of meditation for them was called the Anal-Duccaid (Breath Prayer) and it was usually achieved by creating an internal landscape known as the Cromlech of Meath.
As always, please remember that this is not a complete list. I do not know everything. The internet namely had sources for Irish Celtic beliefs and mythology.