Thread:Redfork2000/@comment-30384301-20180925062435/@comment-26888167-20181112030300

Discord isn't immune to pain. The thing is that no one has actually managed to hurt him, because he'll always stop the attack before it happens. This time, however, not even Discord knew this attack existed.

For example if Ink Splash turned giant and tried to smash Discord, Discord would simply stop her from doing it, whether it be be shrinking her to the size of an ant, of teleporting out of the way, or transforming himself into a giant spike to hurt Ink Splash when she steps him. In any case, he doesn't take damage because he counters the attack with his own tricks. However, if Discord allowed Ink Splash to smash him without countering it, he would definitely take damage.

The same logic applies here. Discord didn't know Captain Dark Shell was capable of this kind of attacks, and therefore, wasn't able to counter it.