Gronw Pebr is a warrior

Warrior

A warrior is a person skilled in combat or warfare, especially within the context of a tribal or clan-based society that recognizes a separate warrior class.-Warrior classes in tribal culture:...

, hunter and antagonist

Antagonist

An antagonist is a character, group of characters, or institution, that represents the opposition against which the protagonist must contend...

 in Welsh tradition

Welsh mythology

Welsh mythology, the remnants of the mythology of the pre-Christian Britons, has come down to us in much altered form in medieval Welsh manuscripts such as the Red Book of Hergest, the White Book of Rhydderch, the Book of Aneirin and the Book of Taliesin....

, appearing primarily in the fourth branch of the Mabinogi

Four Branches of the Mabinogi

The Four Branches of the Mabinogi are the best known tales from the collection of medieval Welsh prose known as the Mabinogion. The word "Mabinogi" originally designated only these four tales, which are really parts or "branches" of a single work, rather than the whole collection...

as the lord of Penllyn

Penllyn

Penllyn is a former civil parish in the Welsh county of Gwynedd. The parish was created in 1894 from the part of Criccieth parish that lay outside the ancient borough. It was abolished in 1934, and divided between Llanystumdwy and Criccieth....

, the lover of Blodeuwedd

Blodeuwedd

Blodeuwedd or Blodeuedd, , is the wife of Lleu Llaw Gyffes in Welsh mythology, made from the flowers of broom, meadowsweet and the oak by the magicians Math and Gwydion, and is a central figure in the fourth branch of the Mabinogi.-Role in Welsh tradition:The...

 and the murderer of Lleu Llaw Gyffes

Lleu Llaw Gyffes

Lleu Llaw Gyffes is a hero of Welsh mythology. He appears most prominently in the Fourth Branch of the Mabinogi, the tale of Math fab Mathonwy, which tells the tale of his birth, his marriage, his death, his resurrection and his accession to the throne of Gwynedd...

. He is also mentioned in the Welsh Triads

Welsh Triads

The Welsh Triads are a group of related texts in medieval manuscripts which preserve fragments of Welsh folklore, mythology and traditional history in groups of three. The triad is a rhetorical form whereby objects are grouped together in threes, with a heading indicating the point of likeness...

 and in the medieval poem Cad Goddeu

Cad Goddeu

Cad Goddeu is a medieval Welsh poem preserved in the 14th-century manuscript known as the Book of Taliesin. The poem refers to a traditional story in which the legendary enchanter Gwydion animates the trees of the forest to fight as his army...

.

Role in Welsh tradition

Lleu Llaw Gyffes

Lleu Llaw Gyffes

Lleu Llaw Gyffes is a hero of Welsh mythology. He appears most prominently in the Fourth Branch of the Mabinogi, the tale of Math fab Mathonwy, which tells the tale of his birth, his marriage, his death, his resurrection and his accession to the throne of Gwynedd...

 has been placed under a tynged

Tynged

A tynged is the Welsh equivalent of the Irish geis, the most famous of which were those that Arianrhod placed on her son Lleu Llaw Gyffes in the fourth of the Four Branches of the Mabinogi, the Mabinogi of Math fab Mathonwy....

 that he would never gain a wife of human birth. His uncle, the trickster

Trickster

In mythology, and in the study of folklore and religion, a trickster is a god, goddess, spirit, man, woman, or anthropomorphic animal who plays tricks or otherwise disobeys normal rules and conventional behavior. It is suggested by Hansen that the term "Trickster" was probably first used in this...

 and magician Gwydion

Gwydion

Gwydion fab Dôn is a magician, hero and trickster of Welsh mythology, appearing most prominently in the Fourth Branch of the Mabinogi, which focuses largely on his relationship with his young nephew, Lleu Llaw Gyffes...

 joins forces with the Venedotian

Kingdom of Gwynedd

Gwynedd was one petty kingdom of several Welsh successor states which emerged in 5th-century post-Roman Britain in the Early Middle Ages, and later evolved into a principality during the High Middle Ages. It was based on the former Brythonic tribal lands of the Ordovices, Gangani, and the...

 king Math fab Mathonwy to create a woman for Lleu, out of the flowers of the oak, the broom and the meadowsweet, naming her Blodeuwedd

Blodeuwedd

Blodeuwedd or Blodeuedd, , is the wife of Lleu Llaw Gyffes in Welsh mythology, made from the flowers of broom, meadowsweet and the oak by the magicians Math and Gwydion, and is a central figure in the fourth branch of the Mabinogi.-Role in Welsh tradition:The...

. One day, while Lleu is away on business, Gronw Pebr, lord of Penllyn, comes across Lleu's stronghold whilst out hunting and falls in love with Blodeuwedd. They conspire to kill Lleu so that they can be together.

Lleu can only be killed if certain conditions are met, and Blodeuwedd tricks him into revealing what these conditions are. He can not be killed indoors or outdoors, on horseback or on foot. Consequently he can only be killed whilst he has one foot on a cauldron

Cauldron

A cauldron or caldron is a large metal pot for cooking and/or boiling over an open fire, with a large mouth and frequently with an arc-shaped hanger.- Etymology :...

 and one on a goat (the cauldron being placed on a stream bank but under a roof) and by someone using a spear forged over a year and only when people are attending mass.

Blodeuwedd coaxes the secret from Lleu and a year later, Gronw ambushes the prince. He flings the spear at Lleu, who disappears in the form of an eagle

Eagle

Eagles are members of the bird family Accipitridae, and belong to several genera which are not necessarily closely related to each other. Most of the more than 60 species occur in Eurasia and Africa. Outside this area, just two species can be found in the United States and Canada, nine more in...

. Gronw and Blodeuwedd now assume power, but on hearing the news of his nephew Gwydion sets out to find and cure him. He finds Lleu in the form of a wounded eagle

Eagle

Eagles are members of the bird family Accipitridae, and belong to several genera which are not necessarily closely related to each other. Most of the more than 60 species occur in Eurasia and Africa. Outside this area, just two species can be found in the United States and Canada, nine more in...

 perched in an oak

Oak

An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...

 tree and restores him to human form.

Together they overcome Gronw, and make him stand in the same position that Lleu occupied when Gronw flung the spear at him. Gronw is allowed to hold a stone as a shield, but Lleu throws the spear so hard that it penetrates the stone and kills Gronw. Gwydion curses Blodeuwedd, turning her into an owl

Owl

Owls are a group of birds that belong to the order Strigiformes, constituting 200 bird of prey species. Most are solitary and nocturnal, with some exceptions . Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish...

.