Question: Princess Eilonwy, is a fictional character in Lloyd Alexander's "The Chronicles of Prydain", she also appears  in four of the five novels in the series, as well as Disney's 1985 animated film adaptation of which 1985 American animated dark fantasy adventure film?

Context articles: The Chronicles of Prydain
The Castle of Llyr
Princess Eilonwy
Taran (character)
Fflewddur Fflam
Gwystyl
The Black Cauldron (film)
Gurgi
Susan Sheridan
The Book of Three

The Chronicles of Prydain is a pentalogy of children's high fantasy Bildungsroman novels written by American author Lloyd Alexander.
 Henry Holt published one annually from 1964 to 1968; the second earned a 1966 Newbery Honor and the last won the 1969 Newbery Medal.
The Castle of Llyr (1966) is a high fantasy novel by Lloyd Alexander, the third of five volumes in "The Chronicles of Prydain".
 The story continues the adventures of Taran "Assistant Pig-Keeper", primarily on the Isle of Mona west of Prydain, far from the forces of Arawn, Lord of Death.
Princess Eilonwy, later known as Queen Eilonwy ( ), is a fictional character in Lloyd Alexander's "The Chronicles of Prydain".
 She appears in four of the five novels in the series, as well as Disney's 1985 animated film adaptation "The Black Cauldron".
 Eilonwy is a member of the Royal House of Llyr, and the women in her line are formidable enchantresses, including her mother Angharad and grandmother Regat.
 She has inherited this characteristic, most readily visible in her manipulation of a magical item she calls her "bauble", a small golden sphere that glows with magical light when activated by her willpower.
 Eilonwy's father, Geraint, was a commoner with whom her mother fell in love.
Taran is a fictional character from Lloyd Alexander's "The Chronicles of Prydain" series of novels.
 Serving as the series's central protagonist, he is first introduced as the assistant pig-keeper at Caer Dallben charged with the care of Hen Wen, the oracular white pig.
 With dreams of becoming a great hero, over the course of the series, his character matures as he is drawn into the war against Arawn Death-Lord and his champion, the Horned King.
Fflewddur Fflam, son of Godo, is a cantrev lord in the fictional country of Prydain in Lloyd Alexander's Chronicles of Prydain.
 He is referred to as a King, but makes it perfectly clear that he is a very minor king of a tiny kingdom at best, much less important than the High King who is the ruler of Prydain.
 His kingdom is described as being dreary and dull.
 As a result, he often leaves it to go wandering about as the world's most unofficial bard in the mystical land of Prydain.
 Though he returns from time to time to rule, he once mentions that he gets the feeling that the people of his country get along just fine even if he is not there.
Gwystyl is a character in Lloyd Alexander's fantasy "Chronicles of Prydain" book series.
 He first appears as one of the Fair Folk in the second novel of the series, "The Black Cauldron".
 He also makes an appearance in the fifth and final novel, "The High King."
The Black Cauldron is a 1985 American animated dark fantasy adventure film produced by Walt Disney Feature Animation in association with Silver Screen Partners II and released by Walt Disney Pictures.
 The 25th Disney animated feature film, it is loosely based on the first two books in "The Chronicles of Prydain" by Lloyd Alexander, a series of five novels that are, in turn, based on Welsh mythology.
Gurgi is a fictional character in "The Chronicles of Prydain", the series of fantasy novels by Lloyd Alexander.
 Gurgi is the hero Taran's faithful companion, appearing in all five books.
Susan Haydn Thomas (March 18, 1947 – August 8, 2015) was a British actress and voice actress.
 Her voice acting roles included Noddy in "Noddy's Toyland Adventures", Princess Sylvia in "Muzzy in Gondoland", Trillian in the BBC radio series "The Hitchhiker's Guide to the Galaxy" and Princess Eilonwy in the animated film "The Black Cauldron".
The Book of Three (1964) is a high fantasy novel by Lloyd Alexander, the first of five volumes in "The Chronicles of Prydain".
 The series follows the adventures of Taran the Assistant Pig-Keeper, a youth raised by Dallben the enchanter, as he nears manhood while helping to resist the forces of Arawn Death-Lord.