Culhwch's appeal to King Arthur includes a long catalogue of people whose assistance he invokes. Greid son of Eri appears among them. The expression identifies Greid by his father, preserving a second name inside the first man's description. It does not say that Eri himself sits in Arthur's hall or joins the quest. Nor does it provide his ancestry, occupation or territory. This is a limited but genuine literary connection: Eri is not a modern invention, yet almost everything that could become a conventional biography lies outside what the passage actually tells us.

The same patronymic recurs in the account of Greid's captivity. During the conflict over Creiddylad, Gwyn ap Nudd defeats the opposing host and takes several men prisoner, Greid among them. Arthur later intervenes and secures the captives' release. These are events in Greid's story, not recorded experiences of Eri. Naming the father still helps the audience identify which Greid is meant. The recurrence also corrects the impression that Eri's name appears once and then disappears: he is repeatedly named through his son, even though he never becomes an acting character.

A further reference occurs during the search for Mabon, the son of Modron. The ancient salmon carries Arthur's messengers towards the prison at Gloucester, where Mabon speaks about his suffering and compares it with the imprisonments of Lludd Llaw Ereint and Greid son of Eri. Mabon makes the comparison, not the salmon. The words do not place all three men together in one cell. Nor do they establish a single fixed prisoner-list shared unchanged by every Welsh text. For Eri's entry, the important point is that his son's patronymic is remembered within another hero's account of captivity.

Drudwyn supplies the other major connection. The hound is described as the whelp of Greid son of Eri and is required for the hunt of Twrch Trwyth. Here the possessive identifies the person associated with the dog; it is not a claim that Greid fathered the animal. Eri should therefore not be turned into an ancestor whose blood literally runs in Drudwyn. The hunting requirements and special equipment belong to the wider quest. They can explain why Greid's name is repeated, but they offer no evidence that Eri was himself a breeder, huntsman or participant in the chase.

It is possible that some names in the tale once carried associations no longer recoverable to us. Eri's brief appearance, however, cannot prove that he had a complete lost romance, a divine identity or a celebrated career. The most useful account keeps the distinction between an attested relationship and an imagined life. Through Greid and the hound Drudwyn, the name remains connected with the captives, rescuers and hunters of Culhwch and Olwen. These surrounding adventures give the patronymic a place in Arthur's wider world without turning every event into an experience of the otherwise undescribed father. Eri remains a legendary father whose name survives wherever the storyteller identifies his son.