Casimir gritted his teeth at Acacia's last words. He hated it when his opponents had the last laugh, particularly with a threat. That typically emboldened others who had observed such a thing to try their hand against him, making Casimir feel the need of going through his whole little cycle of fear momgering yet again. Unlike Acacia, he didn't hold so much sway over many with just his words. He needed to enforce them, which is why he focused on exploiting the fear of others and make an example of them. That usually kept heat from other potential nuisciances off his back, and ensured that they would not openly divert their mocking eyes to others instead. At least while Casimir was around.
The Slytherin usually did such things because of his parents and family. It wasn't that they specifically goaded him to do such things, but they were very harsh when it came to the respect others had for Casimir. If they found out he simply allowed offenses against himself to go unpunished, he'd get a pretty harsh tongue lashing from them. Naturally though, he was now much too old to really be afraid of such things, but the conditioning still managed to work its magic. Either way, Casimir always felt the innate drive to cause fear in order to establish himself as a respected individual. Now, the whole using fear to protect potential victims was a different story, but Casimir currently didn't feel like thinking through that again.
He looked to the other Slytherins in his table, all of which either averted their gaze from his or simply were off having their own conversations. Ok, well at least none were daring to poke fun at him for what Acacia had ended with. It was true he had been an ally to her in the past, but truth was, he was beginning to hate the girl. More out of envy than anything else, her skill with words was quite astounding he had to admit. Casimir was forced to bite his tongue in secret to keep his expression from changing as Acacia began to talk about how Willow was her friend and was to be left alone, but soon he simply focused on the ceiling above to observe the floating candles amd starry sky. Perhaps he really did have no true reason to be suspicious of her, but at the moment that was not his concern.