Cethern mac Fintain is well pleased with the heroic reading of his wounds by Cú Chulainn and the Ulster physician Fingin. Between them, they tell the tale of his warrior exploits, one of which is the only physical description of Queen Medb in the Táin Bó Cúailnge:

Fingin came to Cethern. He scrutinized him from a distance.

"Examine me," said Cethern. "This first stab I got is painful."

"This is a wanton and arrogant woman's feat of arms," replied Fingin.

"I'd say that's true," said Cethern. "A tall beautiful woman, pale-faced and long-visaged came to me. She had thick fair hair and she wore two golden birds on her shoulder. She had a dark purple hooded cloak overlaid in gold. In her hand was a light javelin, keen and sharp-edged. A sword with knobbed hilt was across her shoulders. Great was her appearance. She was the first to approach me and wound me."

"Glory be!" said Cú Chulainn, "that is Medb of Crúachu!.

(II.3201-10; trans. Ann Dooley, Playing the Hero: Reading the Irish Saga Táin Bó Cúailnge, 2007)

In the Irish saga, Táin Bó Cuailnge (the Cattle Raid of Cooley), a Connacht seer named Fedelm foretells the defeat of Medb's army, which is on a raid in Ulster to capture the magical Brown Bull of Cuailnge. The Tain describes her and the clothes she is wearing when she meets Medb as follows:

Fedelm is a young woman dressed in a speckled cloak held by a gold pin, a tunic with a red-embroidered hood and sandals with gold clasps. She rides in a chariot drawn by two magnificent black steeds. In her hand, she holds a light gold weaving rod. She has yellow hair fashioned in three tresses - two are wound upward, while the third hangs behind her, all the way down to her calves. She has a broad brow and a pointed chin. Her eyebrows are dark, her lashes are long and her teeth shimmer like an array of the whitest gems. But the most amazing apect of Fedelm's features are her eyes: she has triple irises.

Fedelm has the skill of imbas forasnai, or the Light of Foresight. Imbas forasnai is a gift of clairvoyance or divination shared by filidh (the Gaelic poet class described in the old Irish Brehon Laws), where prophecies come to them through certain practices in the form of a vision. Fedelm learned this and other druidical skills in Alba, probably on Skye under the tutelage of the master Celtic martial arts druid Scathach.

Three times, Queen Medb of Connacht asks Fedelm what she see when the seeress looks at her host, and three times she replies, "I see crimson. I see red."

Medb doesn't believe this is possible because she knows the men of Ulster are suffering from the Pangs of Ulster, a curse of five days and four nights thrown on them by Macha.

After her last warning to the queen, Fedelm predicts that the Irish hero Cúchulainn will single-handedly bar their path and delay their march to raid the cattle of Daire Mac Fiachna and his prized bull long enough for the Ulstermen to recover and defeat her army. Despite Fedelm's prophecy and warning, Medb heedlessly marches her army into Ulster and suffers a bloody defeat.