Aned appears only once in all of surviving Welsh literature, in the prose tale Culhwch and Olwen, the earliest extended Arthurian story and the longest of the native Welsh tales. The story survives in the Red Book of Hergest and the White Book of Rhydderch, fourteenth-century manuscripts preserving a far older tale. In this story, Culhwch, a prince cursed by his stepmother to love only Olwen, must win the hand of the giant Ysbaddaden's daughter. Ysbaddaden, knowing that his own death follows his daughter's wedding, sets Culhwch a list of impossible tasks, the greatest of which is the hunt for Twrch Trwyth, a monstrous boar that was once an Irish king named Taredd, transformed by God's punishment into a creature with venom-dripping bristles and a comb, scissors, and razor lodged between its ears.

Among the many wonders Ysbaddaden demands for this hunt are two hounds named Aned and Aethlem. The text gives them no separate histories, no individual owners, no tales of how they came to Arthur's court. They appear as a pair, inseparable in name and function, described as being as swift as a gust of wind and always triumphant when hunting. In a tale where every object and animal has a pedigree and a legend of its own, the fact that Aned and Aethlem appear without backstory suggests that their fame was once so great it needed no explanation. They were simply known, the matched pair whose speed was proverbial across Britain.

The hunt itself is the most elaborate chase in medieval Welsh literature. Arthur and his host sail to Ireland and find Twrch Trwyth guarded by seven piglet-warriors, themselves transformed men. The chase sweeps across Britain like a storm. Arthur's warriors drive the boar from Ireland to Porth Clais in Dyfed, through the Preseli Mountains down to the Severn estuary where Cornish and Devon men join the fray. At every stand the boar turns and slaughters knights and hounds by the dozen, yet Aned and Aethlem keep running, two shadows that never fall behind, their breath mingling in the cold air of the chase.

The climax comes at the mouth of the Severn. The warriors wrest the razor and scissors from Twrch Trwyth as he wades in the river, but the beast touches bottom and bolts away before they can seize the comb. The pursuit continues to Cornwall, where the boar causes more death than in all previous battles combined. Finally Arthur's men drive Twrch Trwyth into the sea. The comb is retrieved, but the boar escapes into the waves. The tale ends with a line that haunts every reader: it was never known from that day onward to what place the boar went, and Aned and Aethlem with him. The two hounds, still running, vanished into the western ocean alongside the quarry they had pursued across three kingdoms.

Aned's legacy is inseparable from that of its fellow hound, yet the name itself hints at something deeper. The Welsh word aned can mean breath or life, and the hound's name may carry this resonance, the breath that drives the chase and the life-force that refuses to stop. Unlike Arthur's own hound Cafall, whose paw-print in stone at Buelt is recorded in the ninth-century Historia Brittonum, Aned leaves no physical trace upon the British landscape. Its monument is the partnership itself, the fact that in the oldest Arthurian tale two hounds were needed where one would not suffice, and that their paired names have survived a thousand years of silence. The companion who is never named alone is sometimes the one who makes the story possible.