1. Emperor Caligula, from Glanert's Caligula

The Roman emperor Caligula became notorious for his tyranny and cruelty. It is said he suggested making his favourite horse a senator, he demanded that executions be as painful as possible and he may have been sleeping with his sister – but then which ancient ruler wasn’t?

Detlev Glanert’s opera, Caligula, is based on Camus’s existential take on the story. After the death of his sister, Caligula comes to the conclusion that life is meaningless and attempts to demonstrate this to his terrified court in a series of sadistic, blackly comic and bizarre scenarios.

As Camus wrote 'he becomes obsessed with the impossible and poisoned with scorn and horror, he tries through murder and the systematic perversion of all values, to practise a liberty which he will eventually discover is not the right one.'

2. Don Giovanni, from Mozart’s Don Giovanni

Womaniser, murderer – or as the opera’s subtitle has it, libertine – Don Giovanni is an amoral character with an eye for things that don’t belong to him. Like the young bride Zerlina who has just got married and presents the Don with a challenge he can’t resist. She doesn’t distract him long, though – and she becomes just one of his ‘catalogue of conquests’.

As the opera continues his enemies – not least a couple of spurned women – close in and it ends with a scene of gravestones, ghosts and hell fire. One of those present at the opera’s first performances in 1787 was Giacomo Casanova. I wonder what he thought of it?

3. Baron Scarpia, from Puccini’s Tosca

Baron Scarpia is an almost pantomime villain – he exploits his powerful position as chief of police in Rome and enjoys toying with Tosca and her lover Cavaradossi before having him executed and trying to rape her.

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Puccini writes some truly melodramatic, hammer-horror music for this character of seemingly undiluted evil – including the chilling Scarpia motif, which is heard at the very opening of the opera and then hangs over the whole work. But he at least gets his comeuppance at the hands of the wronged heroine, Tosca.

4. The witch from Humperdinck’s Hansel and Gretel

For really terrifying characters, look no further than fairytales and folklore, and Humperdinck chose one of the blacker ones for his opera Hansel and Gretel.

The two children of the title are thrown out of the house by their mother after an incident over spilt milk… They come across a house made of gingerbread and sweets in the middle of the forest and merrily go inside at the invitation of the creepy woman (although the part is often played by a man) who lives there. Even the compulsory happy ending can't quite get rid of the taste left by this baddie.

5. Iago from Verdi’s Otello

The poet Samuel Taylor Coleridge called Shakespeare’s Iago a ‘motiveless malignity’ – a character who’s evil without reason. He brings about the downfall not just of the tragic hero, Othello, but also his virtuous wife Desdemona and the innocent bystander Cassio. A scheming snake of a character – who nevertheless manages to seduce the audience as well as the characters on stage.

6. Mephistopheles, Gounod’s Faust

From a character who resembles the devil to one of Satan’s own minions: in Gounod’s Faust the famous doctor of the title conjures Méphistopheles who offers him pleasure and youth, in exchange for his soul.

Faust accepts and the pair embark on an opera’s worth of partying, brawling and seducing – leaving a slew of victims behind, not least Faust's lover Marguérite. Needless to say, Méphistopheles enjoys it all immensely.