Discord GM: Did you warn them?
DM: No. How could I? I didn't even know you were going to do that until you told me.
Discord GM: Still feels like I've been received with a severe under-reaction.
DM: Look, they were generally prepared for you this time. Discord's willingness to deceive and to subvert expectations isn't a surprise anymore.
Discord GM: And what is this "grazed shot" business about?
DM: They worked hard to get to this point – they deserved to be rewarded a little bit for their effort. And you played chicken with six semi-sentient magical artifacts that are full of what is basically your antiparticle.
Discord GM: Heh heh! It /was/ very bold of him, wasn't it?
DM: ...Yeah, yeah it was. Glad you're having fun.
Constantly being unpredictable is its own form of predictability. When your opponent learns to expect the unexpected, you need to mix it up a little. At that point, the last thing they'd expect is playing it straight.
Yerp. And "expecting the unexpected" doesn't even mean predicting the particulars. There comes a time when "we couldn't possibly predict that" starts becoming par for the course. It may still invoke a challenge but it doesn't bring that feeling of awed/angered surprise anymore.
And if you stretch the mastermind trope too much, even frustration can wear thin, leaving only apathy behind. Last thing you want is your new dastardly move being met with indifference, or a resigned "here we go again".
This very feeling is what happened to Q in Star Trek, particularly in voyager, after a while the crew just sighed and asked what it was he wanted this time.
On the other hand, a new dastardly move being met with no more response than a resigned "here we go again" could be the start of a confused, distraught villain's path back to the Light Side. Or the cause of their Ultimate Tantrum of Universal Annihilation, either way.
And this is why I will forever hold that the most chaotic neutral of all beings is Puck, from Gargoyles. A trickster fae who came full circle to disguising himself as the most boring straight-man assistant ever devised and living the role every second he could, because it was the funniest thing he could possibly think of!
Today on "none of these words should make sense together": "You played chicken with six semi-sentient magical artifacts that are full of what is basically your antiparticle."