“Scathach’s themes are sports, strength, excellence, kinship, art, tradition, magic, protection and victory. Her symbols are Tartans (plaids) and Celtic music. This Celtic mother figure endows strength, endurance and the ability to ‘go the distance’ no matter our situation. In Scotland She is also a warrior Goddess who protects the land using magic as a weapon, as implied by the translation of Her name, ‘she who strikes fear.’ Warriors from around Scotland were said to have studied under Scathach to learn battle cries and jumping techniques (possibly a type of martial art).
In Scotland, the second weekend in July marks the gathering of Scottish clans to revel in their heritage through numerous games of skill, strength and artistry (including bagpipe competitions). If you have any Scottish or Celtic music, play it while you get ready to energize your whole day with Scathach’s perseverance. If you don’t have the music, for a similar effect find something to wear with a Scottish motif, like heather perfume, a plaid tie, things bearing the image of a thistle or sheep or anything woolen.
To make a Scathach amulet to protect your home, car or any personal possessions, begin with a piece of plaid cloth and put some dried heather in it (alternatively, put in several strands of woolen yarn). Tie this up an keep it where you believe her powers are most needed.”
(Patricia Telesco, “365 Goddess: a daily guide to the magic and inspiration of the goddess”.)
“Scáthach (pronounced scou’-ha, or skah’-thakh) is a figure in the Ulster Cycle of Irish mythology. She is a legendary Scottish warrior woman and martial arts teacher who trains the legendary Ulster hero Cú Chulainn in the arts of combat. Texts describe her homeland as Scotland (Alpae); she is especially associated with the Isle of Skye, where her residence Dún Scáith (Fort of Shadows) stands.”  Other sources say she lived in the Alps.
Scathach is said to be the daughter of Ard-Greimne and Lethra.  “Aoife, another fierce warrior queen, is reputed to be her sister, while Uathach, her daughter, is a fellow teacher at her school. She also has two sons named Cet and Cuar from an unnamed man and trains them within a secret yew tree. Another source tells that she is mother to three maidens named Lasair, Inghean Bhuidhe and Latiaran, the father being a man named Douglas.” 
Patricia Monaghan tells us that Scathach, “the ‘shadowy one’, lived on an island near Scotland and was the greatest female warrior of her time. Heroes from all the Celtic nations would travel to study with her, for she alone knew the magical battle skills that made them unconquerable: great leaps and fierce yells, which seem in ancient legend like puzzled accounts of Oriental martial arts.
“Scathach initiated young men into the arts of war, as well as giving them the ‘friendship of her thighs’, that is to say, initiating them sexually.” 
One of her most famous students was the Irish warrior Cú Chulainn. When the princess Emer sized him up as a possible husband, she thought him too unskilled in his profession; therefore, she suggested he study with Scathach, the foremost warrior of her day. While Cú Chulainn was away, he learned more than martial arts, for through an affair with Scathach’s enemy, Aífe, the warrior produced a son [Connla] whom he late unwittingly killed” (p. 275).
Another account states that “As part of his training Cú Chulainn helped Scáthach overcome a neighbouring female chieftain, Aífe or Aoife (who by some accounts was also Scáthach’s sister), and forced her to make peace, in the process fathering a son by Aífe. Cú Chulainn also ended up sleeping with Scáthach’s daughter Uathach, whose husband Cochar Croibhe he then killed in a duel. On completion of his training, Scáthach also slept with Cú Chulainn.
By some accounts Scáthach was also a formidable magician with the gift of prophecy. She also, again by some accounts, became the Celtic Goddess of the dead, ensuring the passage of those killed in battle to Tír na nÓg, the Land of Eternal Youth and the most popular of the Otherworlds in Celtic mythology.” 
Merriam-Webster’s Encyclopedia of World Religions, “Scáthach“.
Monaghan, Patricia. The New Book of Goddesses and Heroines, “Scathach”.
Wille, Almut. Encyclopedia Mythica, “Scathach“.
Bedford, Tony. Préachán Fuilteach, “Cú Chulainn“.
Ellis, Peter Berresford. Celtic Myths and Legends, “The Shadowy One” (p. 235 – 243).
Parke, Cate & Lisa Campbell. Celtic Queens, “Scáthach and the Defeat of Aoife“.