To prevent Avidius from easily breaking through the ice dagger by drawing out his limbs upward and getting himself free, Sango crafted out the top of each ice dagger like flowers with several branches, like he did when he had the ice dagger go through his palm.
If Avidius tries to get up by pulling his limbs off of it, he would need to try really hard, and still end up creating not just a single hole in all four limbs, but a flower with branches shaped hole.
Getting out with an hole like that would result in extreme blood loss which would end up killing him.
It is a choice of how he wants to die? By dying of extreme blood loss or answering Sango's question before he grants him the mercy referred to as death.
"You have my city hostage and you question why I would come for you?".
Despite what had been done to his body, Avidius did not scream or show any signs of discomfort on his face.
RainbowBeheader Thank you for the gift