Hereric was a prince of the royal family of Deira (approximately modern Yorkshire) in the early seventh century. What do we know about him?
In the following year, that is the year of our Lord 680, Hilda, abbess of the monastery of Streaneshalch, of which I have already spoken, a most religious servant of Christ, after an earthly life devoted to the works of heaven, passed away to receive the reward of a heavenly life, on the seventeenth of November, at the age of sixty-six.
She was nobly born, the daughter of Hereric, nephew to King Edwin
Her life was the fulfilment of a dream which her mother, Breguswith, had when Hilda was an infant, during the time that her husband, Hereric was living in banishment under the protection of the British king Cerdic, where he died of poison. In this dream she fancied that he was suddenly taken away, and although she searched everywhere she could find no trace of him. When all her efforts had failed, she discovered a most valuable jewel under her garments; and as she looked closely, it emitted such a brilliant light that all Britain was lit by its splendour. This dream was fulfilled in her daughter...
--Bede, Book IV Ch. 23.
Cerdic is a variant spelling of Ceretic or Ceredig.
616 Ceredig died.
617 Edwin begins his reign
--Annales Cambriae, available online
Edwin, son of Alla, reigned seventeen years, seized on Elmete, and expelled Cerdic, its king.
--Historia Brittonum, ch. 63, available online
Hereric was clearly the son of a sibling of King Edwin (Eadwine), but it is not known whether he was the son of a sister or a brother. The identity of his other parent is unknown.
Bede does not specify Hereric's age or year of birth. However, since he tells us that Hereric's daughter Hild died on 17 November 680 at age 66 years, Hild must have been born between 18 November 613 and 17 November 614. Hereric must therefore have been old enough to father children by early 614 at the latest. Caveat that this calculation assumes that Bede's dates are accurate and that age was reckoned in complete years incremented on the anniversary of birth, as is the case now - if age was reckoned differently, e.g. by incrementing at a particular season or date rather than on the anniversary of birth, the margin of error might be a year or so either way.
Hild also had a sister Hereswith (Bede, Book IV ch.23). If Hereswith was also Hereric's daughter, as seems likely from the 'H' alliteration of all three names, and if she was born before Hild (see below for rationale), Hereric would have to have been old enough to father children at least a year earlier, in 613 at the latest. Hereric must therefore have been born around 599 at the earliest (making him 14 when he fathered the first of his daughters), and probably some years before then.
If Breguswith's dream that her husband was 'suddenly taken away' is intended to represent his death, and if finding a jewel 'under her garments' is intended to signify that she was pregnant with Hild at the time, this may indicate that Hild was born after Hereric's death. Bede says that Breguswith had the dream when Hild was an infant, implying that Hild was born some time before her mother's dream, although Hereric's death could have occurred before both Hild's birth and Breguswith's dream. Either way, the implication seems to be that Hild was at most an infant when Hereric died. If Hild was born close to the date of her father's death, this further implies that Hild's sister Hereswith was probably born before Hild. As Hild was born some time between late 613 and late 614, this suggests that Hereric's death was some time in 614.
Bede says that Hereric was poisoned. This may be deliberate poisoning, or it may be that a sudden death from natural causes was interpreted as poison. Accidental food poisoning from something like botulism can be fatal, as can acute infections, especially in an era without access to antibiotics. Allergic reactions such as anaphylactic shock could also be interpreted as poisoning.
Hereric was living in exile at the time of his death, at the court of a Brittonic king called Cerdic or Ceretic. It is not known whether he had been resident there a long time or had only recently arrived. Bede says he was living there in banishment, and it is likely that Hereric was expelled from Deira when it was annexed by King Aethelferth of Bernicia (probably in 605, see article 'Dating the annexation of Deira' for the rationale for the date). Bede's statement that Hereric was under the protection of the king implies that he was there with Ceretic's knowledge and consent. Bede doesn't name Ceretic's kingdom, but Historia Brittonum records a Ceretic as King of Elmet contemporary with the reign of Hereric's uncle Edwin (617-633). It seems likely that this Ceretic of Elmet is the same individual as the Ceretic at whose court Hereric was living.
Elmet was a territory in the area around modern Leeds (see sketch map), and the name of the kingdom survives in a few place names such as Sherburn-in-Elmet and Barwick-in-Elmet (see map links below for location). It bordered Hereric's homeland of Deira on the south-west. Hereric's reason for being in Elmet when he met his death in around 614 is not known. He may have been living there in exile ever since Aethelferth annexed Deira, perhaps reflecting personal or family connections with Elmet, or he may have only recently arrived in Elmet, perhaps in the hope of gaining support for an attempt to reclaim Deira, or any number of other possibilities. If Hereric was intending to challenge Aethelferth for Deira, this may suggest a motivation for someone to poison him (if his death was not due to natural causes, see above). Aethelferth would have had an obvious motive to have Hereric assassinated, and no great distance to send an agent to do it. Alternatively, Ceretic, or someone else in Elmet, might have decided that Hereric was too dangerous to have as a guest and arranged to get rid of him. If Hereric was poisoned, as Bede says, there is a plausible political context for murder. Murder, or believed murder, would also be consistent with political developments a few years after Hereric's death (more on this in another article). Needless to say, other interpretations are possible.
Annales Cambriae, available online
Bede, Ecclesiastical history of the English people. Translated by Leo Sherley-Price. Penguin Classics, 1968, ISBN 0-14-044565-X.
Historia Brittonum, ch. 63, available online