Alain le Gros, Alain li Gros, Alain Gros, Alain, Alein, Alan, or Alain the Thickset (Fat) (Welsh: Alain Evrawg  ) was a Fisher King in Grail literature. He features in Robert de Boron 's Joseph d'Arimathie (Estoire del Saint Graal) , a work that was written around the end of the 13th century along with the later Didot Perceval and Perlesvaus . Like many ancient stories, Alain has an historical basis of an existing person, but his history was later embellished through retelling into a allegorical, mythological character with mystical aspects.  
According to de Boron, Alain was the youngest son of Bron and Enygeus, who was made to rule over his brothers and sisters. Alain was Bron's successor as the Keeper of the Grail.  In the Didot Perceval he is said to have been the Father of Perceval and was told by the Holy Spirit that he was destined to become the father of the Grail King. 
In Perlesvaus, Alain le Gros married to Yglais, the son of Garis le Gros and the grandson of Nicodemus . Alain is left the care of the Grail by Josephus, the son of Joseph of Arimathea after he died. Alain uses the Grail to cure King Calafes of the Land Beyond an is baptized, changing his name to Alphasan. Alphasan has his daughter marry Alain's brother Joshua and builds him a new castle called Corbenic , meaning "Holy Vessel" to house the Grail. Their descendents were to rule in the Land Beyond , from Corbenic Castle, until the time of King Pelles, a direct descendend of Joshua and the last Grail King of Corbenic. 
Yglais brother the Lord of the Moors and King of Castle Mortal who is described as wicked, warred upon the Fisher King over possession of the Grail. Alain is killed, Yglais widowed and the castle falls until Perceval returns to conquer it. The Fisher King is buried in an adorned sepulchre where every night a bright light was said to have been seen, surrounding his tomb. 
In another version, Alain remains single while his eleven brothers marry, he is given to Joseph of Arimathea by Bron and his wife. Joseph prays to the grail and is told by an Angel to instruct Alain about Jesus Christ 's death and on religious instrction for him to pass to others. Alain is told to go westwards as far as possible and then leads his brethren to distant lands, preaching the works of Christ and eventually settling in the Vale of Avalon in Glastonbury , Somerset .