The wicked Voltan kills his own father when the latter refuses to turn over the magic of the "last elven mindstone". Before the old man dies, he bequeaths a great sword with a pommel shaped like a human hand to his other son, Hawk. The hand comes to life and grasps the mindstone. The sword is now imbued with magical powers and can respond to Hawk's mental commands. Hawk then vows to avenge his father by killing Voltan.
Voltan's evil touches the whole countryside. Some time later, a man named Ranulf arrives at a remote convent. Ranulf tells the nuns that he survived Voltan's attack on his people, which resulted in the brutal deaths of women and children. Ranulf was seriously injured in the attack. The nuns nurse him back to health, but his hand cannot be saved. Voltan appears at the convent and kidnaps the Abbess, demanding a large sum of gold as a ransom. After Voltan and his henchmen leave with the Abbess,the nuns tell Ranulf to seek the High Abbot at the Fortress of Canterbury. The High Abbot sends Ranulf with a token to find Hawk.
Hawk discovers Ranulf with the help of a local sorceress, a woman whom he defended from an accusation of witchcraft. Ranulf has been captured by brigands, but Hawk rescues him. Ranulf convinces Hawk to rescue the Abbess. After a long and dangerous journey, Hawk locates his old friends: Gort, a dour giant who wields a mighty mallet; Crow, an elf of few words who wields a deadly bow; and Baldin, a wisecracking dwarf, skilled with a whip. The five men arrive at the convent, protecting the nuns and devising a way to lure Voltan into a trap. They use their combined skills to steal gold from a slave trader with which to pay the ransom.
Hawk doubts that Voltan will free the Abbess after the ransom is paid. He explains that Voltan treacherously murdered Hawk's wife, Eliane. Hawk and his friends decide to rescue the Abbess, but they fail. Hawk kills Voltan's son Drogo, who had previously assaulted the convent. Enraged, Voltan confronts the heroes in a final battle at the convent. A rogue nun helps Voltan capture the heroes; Voltan repays her by murdering her. With the help of the sorceress, the heroes escape, but the dwarf is mortally wounded.
In the subsequent battle, Hawk exacts his revenge on Voltan and the Abbess is rescued. An evil entity decides that Voltan will be restored to life to carry out further evil. Heeding the sorceress' advice, Hawk and Gort travel south to continue their battle against evil.
A possible 1981 sequel was referred to in the US magazine Cinefantastique (Fall 1980 Issue) but never made. The director is quoted as saying "...I'll be going on a trip looking for locations for the next one. Whether ITC does it or not, we will be making HAWK - THE DESTROYER in February '.
In 2015 a sequel titled Hawk the Hunter was reported to be in development with a budget of $5 million. There was an unsuccessful attempt to raise some of the money via crowdfunding on Kickstarter. The intended beginning of filming in late 2015 has been postponed. In addition to the sequel, British video game company Rebellion Developments plan to release a game and comic books and director Terry Marcel has plans for a TV series called Hawk the Destroyer.
The film serves as the inspiration for the first track on Flight of the Griffin, the first album by the U.S. band Griffin, released in 1984 by Shrapnel Records. The bassist on the album, Thomas "Hawk" Sprayberry, also takes his nickname from the film.
A quote from the film is referenced in Nothin's Gonna Stop Us the second track on the album Hot Cakes performed by the U.K. band The Darkness.
The film has developed a cult following over the years. Bill Bailey, Simon Pegg. and rock musician Rick Wakeman are fans of the film.
Several references to the film appear in the second series of the British sitcom Spaced.