Less a movie than a two-hour explosion in a special-effects factory, “Maleficent: Mistress of Evil” is a sequel even more unnecessary than most. The title isn’t even accurate: the real villainess this time around is Ingrith (Michelle Pfeiffer), the nasty queen of the kingdom of Ulstead, who aims to destroy the now relatively nice Maleficent and annex her fairy realm, the Moors. But one supposes “Ingrith: Mistress of Evil” wouldn’t have drawn devotees of the first movie on that first, all-important weekend.

The screenplay contrived by Disney stalwart Linda Woolverton (her last effort was the dreadful “Alice Through the Looking Glass”) and helpers Noah Harpster and Micah Fitzerman Blue (who wrote the upcoming “A Beautiful Day in the Neighborhood”) is set five years after the first installment. The Moors is now a happy place inhabited by all sorts of fairies, trolls, and giant tree-people, including the three creepy-looking sprites Knotgrass (Imelda Stanton), Thistlewit (Juno Temple) and Flittle (Lesley Manville) from the last picture. Aurora (Elle Fanning) is now its queen, and her godmother Maleficent (Angelina Jolie) its protector against human violators.

Having taken his time to think about the matter, it appears, Prince Phillip (Harris Dickinson, replacing Brenton Thwaites) of Ulstead, the quasi-medieval human realm just across the river, finally decides to propose to Aurora, who accepts and gets Maleficent’s grudging approval. Phillip, a dim but handsome stiff, is, among other things, serving the wishes of his father King John (Robert Lindsay), a peace-loving fellow who dreams of achieving amity between his kingdom and the Moors and sees the marriage as contributing to that end.

But Henry’s wife Ingrith feels much differently. She secretly aims to eradicate the inhabitants of the Moors, employing her de-fairied lackey Lickspittle (Warwick Davis) to stockpile weapons made of their kryptonite, iron, and her minions Gerda (Jenn Murray) and General Percival (David Gyasi) to spearhead a devastating final assault. She will use the marriage preparations to drive a wedge between Aurora (who frankly doesn’t seem any brighter than her intended) and her godmother, and place blame on the latter for laying a sleeping curse on her husband, though it is actually she who attacks him with the spindle of the spinning-wheel Maleficent had devised against Aurora so many years before.

Ingrith’s scheme seems to work, and Maleficent is sent to an apparently watery grave with an iron bullet. But she’s saved by another winged fairy, Conall (Chiwetel Ejiofor), who has gathered his kind in an underground cavern where they can live free from the danger of the humans who seek to annihilate them. The more hotheaded among them, notably brooding Borra (Ed Skrein), will eventually decide to attack Ulstead, and after a long and frankly boring battle in which many of his companions are mowed down, Maleficent finally intervenes to save the day, although at great personal sacrifice which—as is obligatory in such fantasies—turns out to be reversible, and in an especially risible way.

None of this nonsense taxes the cast. Jolie looks as though she been sprayed-painted alabaster for the title role, and gets barely a mild chuckle for her supposedly strenuous efforts to add some human charm to Maleficent’s naturally forbidding personality, while Fanning successfully makes Aurora come across like a simpering drip. Ejiorfor is saddled with most of the extraordinarily dull message portions of the script, about the brutality of humans and the pain of underdogs abused by them, and none of the other members of his group—who resemble nothing more than Vultan’s Hawkmen from the old “Flash Gordon” stories—make much more than a fleeting impression. The attempt to give Sam Riley’s Diaval—Maleficent’s shape-shifting lieutenant—duties as both comic relief and hero fall flat, and the hideous effect of pasting the faces of Staunton, Temple and Manville onto tiny fairy bodies is as gruesome as it was the first time around; Dickinson comes across like a mannequin, and Lindsay an affable bumbler. As for Pfeiffer, she drips venom from the very start and only increases the steely nastiness to the very end. She wears her gowns and jewels well, though.

One shouldn’t be too harsh about the work of director Joachim Rønning, who’s reduced to the role of traffic cop in a piece like this, but editors Laura Jennings and Craig Wood must take blame for the sluggishness of the expository sequences and the confusedly hectic tone of many of the action ones. It’s hard to gauge the quality of Henry Braham’s cinematography overall, since the visuals are so often overwhelmed by the CGI; but Ellen Mirojnick’s costumes are certainly eye-catching, though Patrick Tatopolous’ production design too often has the appearance of cheesy model work. Geoff Zanelli’s score tries to puff things up mechanically, and the effects are extremely variable—some good, others mediocre, and most tiresome.

Among these blowsy Disney sort-of-live-action extravaganzas, “Maleficent: Mistress of Evil” falls into the same category as last year’s bomb, “The Nutcracker and the Four Realms,” as well as “Alice Through the Looking-Glass.” It’s a poorly written piece, encumbered by an avalanche of effects, that exhausts rather than exhilarates. A dose of Geritol might be prescribed for the franchise; the over-the-counter elixir has plenty of iron in it, which is just what Maleficent needs.