In Welsh myths, when the people of northern Wales offended the fairies, the fairies unleashed an army of monsters. It included a huge toad with sharp claws, a serpent with 100 damned souls writhing under its skin, and a 100-headed monster so huge battles could be fought on its jaws.
Jason Kang

In Welsh folklore, the Witches of Caer Lloyw are "maiden hags" skilled in both witchcraft and warfare. They teach combat skills to the Arthurian knight Peredur (the Welsh version of Sir Percival). However, when he discovers that the witches had tormented his relatives, Peredur takes revenge.
Jérôme Lereculey

Owain ap Urien was a 6th-century Brythonic Celtic king who became mythologized as one of King Arthur's champions. In French Arthurian legends, Owain is the son of Morgan le Fey. However, in Welsh legends, he is the son of Modron ("Mother," a fairy mother goddess).
Howard Pyle

In Welsh myths, the giant British king Bran the Blessed was killed in Ireland, and his huge head was carried home. Back in Britain, the head was buried where the Tower of London now stands. As long as the head is there, Britain can't be invaded, but some say King Arthur dug it up.
Peter Diamond

In Welsh myths, the woman Blodeuwedd ("Flower-Faced") was created from the flowers of the broom, meadowsweet, and oak by the wizard Gwydion to marry his ward Lleu. However, Blodeuwedd fell in love with Gronw, and so tried to murder Lleu. So Gwydion turned her into the first owl.
Yuri Leitch

In Wales, the fairy colours are white and gold, making fairies seem akin to beings of light. However, light doesn't always mean good. Hafgan ("Summer White") battles the hero Pwyll while Gwyn ap Nudd ("White, son of Fog") tempts saints and drives people insane.
John Duncan

The most potent magic of the great Welsh magician Gwydion was turning plants into people. He worked with his uncle Math to transform a bunch of flowers into a wife for his ward Lleu Llaw Gyffes, and later turned a grove of trees into an army to fight an invading fairy host.
Dreoilin

Morgan Tud is the head physician of King Arthur's court in early Arthurian legends, healing many of Arthur's warriors. Though Morgan is male, his name is similar to "Morgen," the fairy queen who heals Arthur in Avalon, so some scholars wonder if there is a link between them.

In many versions, Lancelot and Guinevere fall in love when he rescues her from the knight Maleagant. However, in a fragment of an earlier Welsh legend, it's King Arthur's foster brother Kay who rescues her instead. This suggests that maybe Kay was Guinevere's original lover.
Henry Justice Ford

In Welsh legend, the Black Wyrm of the Barrow was a huge serpent that lived in a barrow. Since a barrow is a pagan tomb, some scholars have assumed that the Wyrm was inspired by a pagan god. It was slain by Peredur (Sir Percival), one of King Arthur's most Christian warriors.
Alan Lee

The British King Gwenddoleu ap Ceidio was said to possess a magic gold & silver chess board whose pieces move by themselves and which could play any opponent on its own. This board appears in many King Arthur legends, and it's one of the 13 Treasures of Britain guarded by Merlin.

Yesterday's links:

Drinax
https://gmkeros.wordpress.com/2025/01/27/traveller-drinax-pt-2-have-hazard-suit-will-travel/

Sharing narrative control (a little)
https://www.prismaticwasteland.com/blog/sharing-the-spotlight-is-insufficient

Branwen
https://en.wikipedia.org/wiki/Branwen

Mischievous fey magic
https://blog.d4caltrops.com/2025/01/d100-mischievous-magic-pixie-pranks-or.html

Egyptian themed adventure
https://www.drivethrurpg.com/en/product/505712/lost-tomb-of-the-mummy-lich-1e

Castle Blackmoor
https://thealexandrian.net/wordpress/40789/roleplaying-games/running-castle-blackmoor
https://thealexandrian.net/wordpress/51999/roleplaying-games/running-castle-blackmoor-part-12b-more-lessons-learned-in-blackmoor

Prep
http://vilecultofshapes.blogspot.com/2025/01/adventures-in-prepping.html

The Welsh hero Pryderi was the son of Pwyll, king of Dyfed, and the fairy princess Rhiannon. He was stolen away from his parents as a baby by a mysterious clawed monster, and raised by another family. Due to his fairy heritage, Pryderi grew to adulthood at superhuman speed.

In a Welsh legend, Prince Llywelyn of Wales came home to find his baby son missing and his dog Gelert covered in blood. Believing Gelert had eaten the baby, Llywelyn killed the dog. Then the baby was discovered alive; the blood had been from a wolf Gelert had killed to save him.
Gourlay Steell

King Arthur owned the hound Cavall in Welsh myth. His name is similar to a Latin word for "horse," indicating great size, strength, and speed. While hunting the giant boar Trwyth, Cavall left a permanent footprint on a stone cairn, which is impossible to remove.

In Welsh myths, Morfran was a son of the witch Ceridwen. He was also the ugliest of King Arthur's warriors (with hair like a stag's). This allowed Morfran to survive Arthur's final battle, as enemies were too afraid to fight him (they mistook Morfran for a demon).
Mauro Laurenti

Owain (or "Ywain") was one of King Arthur's warriors. He had a strong bond with animals, and his closest companion was a black lion. In Welsh myths, Owain also commanded the 300 Ravens of Kenverchyn - a host of giant ravens that could destroy almost any human army.

The adar llwch gwin were huge birds (or possibly griffins) in Welsh myth. Drudwas ap Tryffin owned a pair. Just before he dueled King Arthur, Drudwas ordered them to kill the first man to enter the battlefield. However, Drudwas accidentally entered first, so his birds tore him to pieces.

In medieval Welsh legends, fairies look human, and aren't treated as nonhuman by human characters or collectively referred to by any general term (such as "fairy" or "Tylwyth Teg"). It's just implied that maybe these mysterious people with inexplicable magic aren't quite normal.
Alan Lee

In Welsh myths, Merlin buried a great treasure in a golden cauldron inside the Welsh hill Dinas Emrys - where King Vortigern once tried to sacrifice him to build a tower. Only Merlin's heir (who must have blond hair) will be able to find the hidden cavern and claim the treasure.