In the Flight of the Prince chapter of book 6, Snape is able to block Harry's spells, including the Cruciatus Curse, which Harry casts several times against Snape. According to canon, the Unforgivables cannot be blocked. I know that one can resist (Imperius Curse) or endure (Cruciatus Curse) but not block them. So, how was Snape able to do so?

Here are excerpts from the scene:

“Cruc —” (Harry)

But Snape parried the curse, knocking Harry backward off his feet before he could complete it; Harry rolled over and scrambled back up again

“Cruc —” yelled Harry for the second time, aiming for the figure ahead illuminated in the dancing firelight, but Snape blocked the spell again. Harry could see him sneering.

“No Unforgivable Curses from you, Potter!” he shouted over the rushing of the flames, Hagrid’s yells, and the wild yelping of the trapped Fang.

I'll preempt two possible answers:

  1. It has nothing to do with the fact that Harry is casting them verbally. That's the only way we see Unforgivable Curses cast in the books. At any rate, that has nothing to do with the ability to block them.

  2. If you are going to say that Snape's able to block it because Harry did not get to complete the incantation, I'll remind you that based on the series, you don't necessarily need to finish an incantation for a spell for it to start working. There are many instances when a caster's verbal spell is interrupted but the effect of the spell is still produced, like:

From Beyond the Veil chapter of book 5

The words were hardly out of his mouth when the female Death Eater shrieked, “Accio Proph —”

Harry was just ready for her. He shouted “Protego!” before she had finished her spell, and though the glass sphere slipped to the tips of his fingers he managed to cling on to it.




A jet of red light had shot from the end of Bellatrix Lestrange’s wand, but Malfoy had deflected it. His spell caused hers to hit the shelf a foot to the left of Harry and several of the glass orbs there shattered.

With all of that, I'll repeat, do we know why Snape is successful in blocking Harry's Unforgivable Curses?

  • 14
    Is there a quote on unblockableness? I remember that explicitly stated only for the killing curse.
    – Deltharis
    Mar 11, 2015 at 9:30
  • 8
    I'm with @Deltharis - Moody states specifically that, for Avada Kedavra, there's no counter curse and no blocking it. Unless you can provide a quote with someone stating that all the Unforgivable curses carry this property I think the premise of this question is flawed.
    – DavidS
    Mar 11, 2015 at 15:20
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    also it has everything to do with harry casting them verbally, because harry is kind of a trash wizard and he is not able to perform non-verbal spells regularly or effectively at this point in the book, nor really ever as we almost always see him verbally cast. as throughout this book and the next it is repeated harped on that hermiones mastery of non-verbal spells is impressive especially compared to Harry and Ron.
    – Himarm
    Mar 11, 2015 at 19:39
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    your to examples of spells working before being finished are both from death eaters, who are 40+ years old and quite a bit more skilled then Harry, and bellatrix especially is shown to be able to fight completely non-verbally a feat Harry has never accomplished in the book. there is a difference between being skilled non-verbally but using the spell out-loud, as is habit, then barley being able to use anyspell non-verbally to accidentally cast it non-verbally while not finishing the verbal incantation.
    – Himarm
    Mar 11, 2015 at 19:42
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    I think that in your two examples the Death Eater will finish the spell but the interruption is written to show that anouther spell is shouted over it. So it would really be Bellatrix:STUPEFY, Malfoy(simultaneously):NO. I think you do have to complete the spell. Mar 6, 2016 at 19:56

4 Answers 4


The key word in this is "Parried",

1. to ward off a weapon or blow

2 : to evade or turn aside something

Which means he used an attack to deflect or prevent the unforgivable curse. We know that you can't actually stop the curse or dispel the curse, instead Snape, and Mr. Malfoy simply shot another spell to intercept, deflect, or prevent the casting of, the unforgivable curse. Also re-reading the quote about snape, Harry was physically interrupted the first time, as the quote even states

But Snape parried the curse, knocking Harry backward off his feet before he could complete it;

The second time he casts, it's not specific and we can assume by the fact that Harry again did not finish the incantation Snape again hit him with a faster spell that knocked him down, back, hurt him, or in some way incapacitate him to be unable to finish his spell.

  • I'd point out that if you watch the duel in TOotP between V and D they're not simply throwing sparks at each other, they're conjuring and countering spells. Snape could by physically moving or summoning something to block the curse
    – Liath
    Mar 11, 2015 at 13:17
  • The book was explicit. Snape's countering of Harry's spell only TWICE resulted in Harry being knocked to the ground (not including the time Harry wasn't casting a spell or calling Snape a coward). In a book that is extraordinarily descriptive to the last degree, we can assume that if Snape blocked Harry's curse by conjuring something physical, it would have said so. Mar 11, 2015 at 19:16
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    in the example you linked, harry did not finish the spell, either time, and from my remembrance harry was casting sectumsempra at snape repeatedly before this, and as snape had created this spell himself simply dismissing or stopping the spell should be no problem to him. as others have stated, its in question whether the cruciatus curse is even listen in the unblockable category, and as i have stated, and shown, im arguing purely towards prevent-able and parry-able.
    – Himarm
    Mar 11, 2015 at 19:33
  • @Himarm I suggest you reread the chapter and my question, paying special attention to my two points in preemption. In the meanwhile, here's the order of the spells Harry tried to use against Snape: 1- Stunning Spell; 2- and 3- Cruciatus Curse; 4- Incarcerous Spell; 5- Stunning Spell; 6- Impediment Jinx; 7- Sectumsempra Curse and; 8- Levicorpus Jinx. Mar 11, 2015 at 19:51
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    so, only the cruciatus curse twice, both of which were stopped prematurely, seems pretty straight forward to me.
    – Himarm
    Mar 11, 2015 at 20:10

Of the three Unforgivable Curses, only Avada Kedavra was ever said to be unblockable.

When Mad-Eye Moody introduces these curses to Harry's class (Goblet of Fire chapter 14), he leaves the Avada Kedavra killing curse as the last one.

‘Not nice,’ he said calmly ‘Not pleasant. And there's no counter-curse. There's no blocking it. Only one known person has ever survived it, and he's sitting right in front of me.’

He does not claim the same about the other two curses, Imperius and Cruciatus.

  • 1
    This is the correct answer. Its never stated anywhere that Crucio or Imperio were unblockable.
    – GamerGypps
    Aug 3, 2020 at 9:44

The literary use of cut off words in the latter two examples you give are not to suggest that the words were not finished, but that a later action happened mid sentence. As such, the death eater did finish her acquire spell, we the reader just don't hear it. Remember that whispers still count, as we see in the movie atleast when Snape was quietly counter hexing Harrys broom during a match. The same goes with the Bellatrix example.

With the Harry vs Snape example, we are told that there is a difference. Harry is incapacitated and prevented from finishing the spell. This is a common trope, preventing a person from saying the magic words by covering their mouth or knocking them out/down. Works with curse words too (pun totally intended)

  • Several things, first of which, I am talking about the real Harry Potter books, not the non-canonical movies. Who decides whether the caster actually finished the spell or not? You? Or the readers who read exactly what the books say, and not just someone's conjecture? Besides, those were just a few examples of many throughout the books. Anyway, Snape's counterspells "incapacitated" Harry only twice. The other times, as per the book, Snape simply blocked them without Snape's spells having any effect on Harry, so that's hardly incapacitation, isn't it? Mar 11, 2015 at 19:05
  • Then why don't you add those examples?
    – user16696
    Mar 11, 2015 at 20:10
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    @cde he listed them out in order to me, and it appears harry only tried cruciatus curse twice, both of which was included in the question, the other spells hes referring to are normal spells, where the question of block-ability is a non-issue.
    – Himarm
    Mar 11, 2015 at 21:59
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    @MermishEssence: cde is correct. Your example from From Beyond the Veil chapter of book 5 illustrates it clearly: "He shouted 'Protego!' before she had finished her spell", is different from "before she could finish her spell": she did in fact finish it, even though the text breaks mid-utterance to Harry. It's pretty standard stuff and not a matter of "conjecture".
    – Wayne
    Mar 11, 2015 at 23:34
  • @MermishEssence Shame then that although the films are absolutely terrible (and I refer not to removing dialogue in this case - not to mention so many other places) that part is consistent with the book - Severus interrupts Harry and he also points out that he will block it again and again until he (Harry) learns to keep his mouth shut and his mind closed. This of course was also a reminder to Harry to not give up on closing his mind but naturally Harry wouldn't listen to that esp after what just happened.
    – Pryftan
    Sep 12, 2018 at 18:23

I think as a matter of fact that the Cruciatus can not be cast properly from just hatred or anger, and the caster must actually feel a want to see the victim in the pain that the cruciatus curse presents.

  • 3
    Hi, Welcome to Science Fiction & Fantasy SE, if you have any canon sources that can support you answer to make it just that little bit better, you might attract some more attention!
    – Edlothiad
    Dec 6, 2016 at 19:50
  • 4
    I remember Bellatrix saying this when she was fleeing in Ministry atrium. You should definitely add a quote, it will make a strong answer. Dec 6, 2016 at 19:54

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