Since it's for all intents and purposes prepped at least twice, we'll say about 4 inches thick. The prison is in fact Ishtalle and retains all of her inherant abilities. I forgot to put this in the post(I'll edit it in shortly for official purposes if you dont mind) but she cannot morph while acting as a prison, but also disallows other weapons to morph, using magic as a binding agent.

Edit: Yes the blade is primed to stab him through the back and exit the front.