In the First Branch of the Mabinogi, Pwyll mistakenly stumbles into the realm of Annwn and finds white hounds with red ears feeding on a stag. Pwyll chases the hounds off, only to learn that the hounds belonged to Arawn, ruler of Annwn. To pay for the misdeed, Arawn asks Pwyll to trade places with him for a year and a day and defeat Hafgan, Arawn's rival, at the end of this time, something Arawn has attempted but has been unable to do. Arawn, meanwhile, takes Pwyll's place as lord of Dyfed. Arawn and Pwyll become good friends because when Pwyll wore Arawn's shape, he did not sleep with Arawn's wife.
in ThE FIrst brancH of the mABinOgi, PWYLl MistAkeNlY sTumbles into tHe reaLM of annwn anD fINds whITe HounDs With red eArs feeding oN A sTag. pwYll chAseS ThE HouNDS off, only TO LEarn that tHE hounDs bELONgeD to arawn, ruLer Of Annwn. TO PaY for The misDeeD, Arawn Asks pwyll to trAde pLaces with HIm foR a yeAr and a dAy anD defeat HAfGaN, aRawn'S RivaL, aT tHe END of this tIme, SOmEtHinG Arawn Has attEMpTed but HAs bEen UnabLe to do. Arawn, mEaNwHilE takES pwyll's plAcE AS lOrd oF dyfEd. ArawN aNd pwYll becOmE GoOd frienDs BeCause WHen PWylL WoRE AraWn'S shape, He did nOT sleeP with Arawn's wife.