[@Zetsuko]
The natural armor is only really on the arms and legs, as can be seen in the picture since there's a kind of plate covering those. regardless, I have a hard time agreeing to an action that could've killed her if he'd used his sword to stab her chest instead of just pummel it. 

And I've also stated that, once more, you'd at least suffer the tail somewhere, you're just not going to get a clean escape like this, since while a knock to the back of the knees will knock someone prone, it will not stun them enough to keep their other limbs from moving.

Especially since Tysetaz does not have extraordianry speed or anything, while Vreskrr excells in that department, he'd have to catch the tail somewhere which'd leave a good scar, much like being whipped. But that would in turn have Tysetaz flinch making it more of a duel than a hit and run. 

You got one stab. Of course, if you want to keep having done more, I'll also want more. My personal suggestion is to just run past, blade out, shank her, take the tail (which I'll work into my post*) and move on. I just really can't accept this course since you specifically state stunning her, while that's remove the possibility of any action for me, which means I can't really post.

*It'd probably be akin to "she aimed for the back to leave a nasty scar, but when she puts her weight on her wounded leg she collapses, her tail missing it's mark and instead hitting Tysetaz in the knee." It'd cause him to limp for a while, but it wouldn't be any significant damage.