With the confirmational nod from Draco, Pati didn't waste a single second and immediately went through with the reason they are here in the first place. It didn't go according to plan but the objective has been reached nevertheless.
Not one event can go precisely as planned, at least most of them can't.
It's better to do the deeds when the timing is perfect but Pati can't let loose of this timing where Mathian is hurt and busy thinking about the Leecher, right now is a perfect opportunity for him.
Stab!
Mathian spat a mouthful of blood as Pati's whispers penetrated his ears.
Although he has been wary of Pati's group which turns out to be a very strong group, the obedience and no hint of disapproval instill comfort in Mathian's mind. A guy that is very obedient and is always smiling can definitely be reasoned with.
But that's nothing but a huge mistake as the skin of a nice guy is only a cover of a maniac.